3 files changed, 721 insertions, 0 deletions
diff --git a/third_party/rust/clang-sys/build/common.rs b/third_party/rust/clang-sys/build/common.rs
new file mode 100644
index 0000000000..c5e57c61b9
--- /dev/null
+++ b/third_party/rust/clang-sys/build/common.rs
@@ -0,0 +1,319 @@
+// SPDX-License-Identifier: Apache-2.0
+
+extern crate glob;
+
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::env;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+use glob::{MatchOptions, Pattern};
+
+//================================================
+// Commands
+//================================================
+
+thread_local! {
+    /// The errors encountered by the build script while executing commands.
+    static COMMAND_ERRORS: RefCell<HashMap<String, Vec<String>>> = RefCell::default();
+}
+
+/// Adds an error encountered by the build script while executing a command.
+fn add_command_error(name: &str, path: &str, arguments: &[&str], message: String) {
+    COMMAND_ERRORS.with(|e| {
+        e.borrow_mut()
+            .entry(name.into())
+            .or_insert_with(Vec::new)
+            .push(format!(
+                "couldn't execute `{} {}` (path={}) ({})",
+                name,
+                arguments.join(" "),
+                path,
+                message,
+            ))
+    });
+}
+
+/// A struct that prints the errors encountered by the build script while
+/// executing commands when dropped (unless explictly discarded).
+///
+/// This is handy because we only want to print these errors when the build
+/// script fails to link to an instance of `libclang`. For example, if
+/// `llvm-config` couldn't be executed but an instance of `libclang` was found
+/// anyway we don't want to pollute the build output with irrelevant errors.
+#[derive(Default)]
+pub struct CommandErrorPrinter {
+    discard: bool,
+}
+
+impl CommandErrorPrinter {
+    pub fn discard(mut self) {
+        self.discard = true;
+    }
+}
+
+impl Drop for CommandErrorPrinter {
+    fn drop(&mut self) {
+        if self.discard {
+            return;
+        }
+
+        let errors = COMMAND_ERRORS.with(|e| e.borrow().clone());
+
+        if let Some(errors) = errors.get("llvm-config") {
+            println!(
+                "cargo:warning=could not execute `llvm-config` one or more \
+                times, if the LLVM_CONFIG_PATH environment variable is set to \
+                a full path to valid `llvm-config` executable it will be used \
+                to try to find an instance of `libclang` on your system: {}",
+                errors
+                    .iter()
+                    .map(|e| format!("\"{}\"", e))
+                    .collect::<Vec<_>>()
+                    .join("\n  "),
+            )
+        }
+
+        if let Some(errors) = errors.get("xcode-select") {
+            println!(
+                "cargo:warning=could not execute `xcode-select` one or more \
+                times, if a valid instance of this executable is on your PATH \
+                it will be used to try to find an instance of `libclang` on \
+                your system: {}",
+                errors
+                    .iter()
+                    .map(|e| format!("\"{}\"", e))
+                    .collect::<Vec<_>>()
+                    .join("\n  "),
+            )
+        }
+    }
+}
+
+/// Executes a command and returns the `stdout` output if the command was
+/// successfully executed (errors are added to `COMMAND_ERRORS`).
+fn run_command(name: &str, path: &str, arguments: &[&str]) -> Option<String> {
+    let output = match Command::new(path).args(arguments).output() {
+        Ok(output) => output,
+        Err(error) => {
+            let message = format!("error: {}", error);
+            add_command_error(name, path, arguments, message);
+            return None;
+        }
+    };
+
+    if output.status.success() {
+        Some(String::from_utf8_lossy(&output.stdout).into_owned())
+    } else {
+        let message = format!("exit code: {}", output.status);
+        add_command_error(name, path, arguments, message);
+        None
+    }
+}
+
+/// Executes the `llvm-config` command and returns the `stdout` output if the
+/// command was successfully executed (errors are added to `COMMAND_ERRORS`).
+pub fn run_llvm_config(arguments: &[&str]) -> Option<String> {
+    let path = env::var("LLVM_CONFIG_PATH").unwrap_or_else(|_| "llvm-config".into());
+    run_command("llvm-config", &path, arguments)
+}
+
+/// Executes the `xcode-select` command and returns the `stdout` output if the
+/// command was successfully executed (errors are added to `COMMAND_ERRORS`).
+pub fn run_xcode_select(arguments: &[&str]) -> Option<String> {
+    run_command("xcode-select", "xcode-select", arguments)
+}
+
+//================================================
+// Search Directories
+//================================================
+
+/// `libclang` directory patterns for Haiku.
+const DIRECTORIES_HAIKU: &[&str] = &[
+    "/boot/system/lib",
+    "/boot/system/develop/lib",
+    "/boot/system/non-packaged/lib",
+    "/boot/system/non-packaged/develop/lib",
+    "/boot/home/config/non-packaged/lib",
+    "/boot/home/config/non-packaged/develop/lib",
+];
+
+/// `libclang` directory patterns for Linux (and FreeBSD).
+const DIRECTORIES_LINUX: &[&str] = &[
+    "/usr/lib*",
+    "/usr/lib*/*",
+    "/usr/lib*/*/*",
+    "/usr/local/lib*",
+    "/usr/local/lib*/*",
+    "/usr/local/lib*/*/*",
+    "/usr/local/llvm*/lib*",
+];
+
+/// `libclang` directory patterns for macOS.
+const DIRECTORIES_MACOS: &[&str] = &[
+    "/usr/local/opt/llvm*/lib",
+    "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib",
+    "/Library/Developer/CommandLineTools/usr/lib",
+    "/usr/local/opt/llvm*/lib/llvm*/lib",
+];
+
+/// `libclang` directory patterns for Windows.
+const DIRECTORIES_WINDOWS: &[&str] = &[
+    "C:\\LLVM\\lib",
+    "C:\\Program Files*\\LLVM\\lib",
+    "C:\\MSYS*\\MinGW*\\lib",
+    // LLVM + Clang can be installed as a component of Visual Studio.
+    // https://github.com/KyleMayes/clang-sys/issues/121
+    "C:\\Program Files*\\Microsoft Visual Studio\\*\\BuildTools\\VC\\Tools\\Llvm\\**\\bin",
+    // LLVM + Clang can be installed using Scoop (https://scoop.sh).
+    // Other Windows package managers install LLVM + Clang to previously listed
+    // system-wide directories.
+    "C:\\Users\\*\\scoop\\apps\\llvm\\current\\bin",
+];
+
+/// `libclang` directory patterns for illumos
+const DIRECTORIES_ILLUMOS: &[&str] = &[
+    "/opt/ooce/clang-*/lib",
+    "/opt/ooce/llvm-*/lib",
+];
+
+//================================================
+// Searching
+//================================================
+
+/// Finds the files in a directory that match one or more filename glob patterns
+/// and returns the paths to and filenames of those files.
+fn search_directory(directory: &Path, filenames: &[String]) -> Vec<(PathBuf, String)> {
+    // Escape the specified directory in case it contains characters that have
+    // special meaning in glob patterns (e.g., `[` or `]`).
+    let directory = Pattern::escape(directory.to_str().unwrap());
+    let directory = Path::new(&directory);
+
+    // Join the escaped directory to the filename glob patterns to obtain
+    // complete glob patterns for the files being searched for.
+    let paths = filenames
+        .iter()
+        .map(|f| directory.join(f).to_str().unwrap().to_owned());
+
+    // Prevent wildcards from matching path separators to ensure that the search
+    // is limited to the specified directory.
+    let mut options = MatchOptions::new();
+    options.require_literal_separator = true;
+
+    paths
+        .map(|p| glob::glob_with(&p, options))
+        .filter_map(Result::ok)
+        .flatten()
+        .filter_map(|p| {
+            let path = p.ok()?;
+            let filename = path.file_name()?.to_str().unwrap();
+
+            // The `libclang_shared` library has been renamed to `libclang-cpp`
+            // in Clang 10. This can cause instances of this library (e.g.,
+            // `libclang-cpp.so.10`) to be matched by patterns looking for
+            // instances of `libclang`.
+            if filename.contains("-cpp.") {
+                return None;
+            }
+
+            Some((directory.to_owned(), filename.into()))
+        })
+        .collect::<Vec<_>>()
+}
+
+/// Finds the files in a directory (and any relevant sibling directories) that
+/// match one or more filename glob patterns and returns the paths to and
+/// filenames of those files.
+fn search_directories(directory: &Path, filenames: &[String]) -> Vec<(PathBuf, String)> {
+    let mut results = search_directory(directory, filenames);
+
+    // On Windows, `libclang.dll` is usually found in the LLVM `bin` directory
+    // while `libclang.lib` is usually found in the LLVM `lib` directory. To
+    // keep things consistent with other platforms, only LLVM `lib` directories
+    // are included in the backup search directory globs so we need to search
+    // the LLVM `bin` directory here.
+    if cfg!(target_os = "windows") && directory.ends_with("lib") {
+        let sibling = directory.parent().unwrap().join("bin");
+        results.extend(search_directory(&sibling, filenames).into_iter());
+    }
+
+    results
+}
+
+/// Finds the `libclang` static or dynamic libraries matching one or more
+/// filename glob patterns and returns the paths to and filenames of those files.
+pub fn search_libclang_directories(filenames: &[String], variable: &str) -> Vec<(PathBuf, String)> {
+    // Search only the path indicated by the relevant environment variable
+    // (e.g., `LIBCLANG_PATH`) if it is set.
+    if let Ok(path) = env::var(variable).map(|d| Path::new(&d).to_path_buf()) {
+        // Check if the path is a matching file.
+        if let Some(parent) = path.parent() {
+            let filename = path.file_name().unwrap().to_str().unwrap();
+            let libraries = search_directories(parent, filenames);
+            if libraries.iter().any(|(_, f)| f == filename) {
+                return vec![(parent.into(), filename.into())];
+            }
+        }
+
+        // Check if the path is directory containing a matching file.
+        return search_directories(&path, filenames);
+    }
+
+    let mut found = vec![];
+
+    // Search the `bin` and `lib` directories in the directory returned by
+    // `llvm-config --prefix`.
+    if let Some(output) = run_llvm_config(&["--prefix"]) {
+        let directory = Path::new(output.lines().next().unwrap()).to_path_buf();
+        found.extend(search_directories(&directory.join("bin"), filenames));
+        found.extend(search_directories(&directory.join("lib"), filenames));
+        found.extend(search_directories(&directory.join("lib64"), filenames));
+    }
+
+    // Search the toolchain directory in the directory returned by
+    // `xcode-select --print-path`.
+    if cfg!(target_os = "macos") {
+        if let Some(output) = run_xcode_select(&["--print-path"]) {
+            let directory = Path::new(output.lines().next().unwrap()).to_path_buf();
+            let directory = directory.join("Toolchains/XcodeDefault.xctoolchain/usr/lib");
+            found.extend(search_directories(&directory, filenames));
+        }
+    }
+
+    // Search the directories in the `LD_LIBRARY_PATH` environment variable.
+    if let Ok(path) = env::var("LD_LIBRARY_PATH") {
+        for directory in env::split_paths(&path) {
+            found.extend(search_directories(&directory, filenames));
+        }
+    }
+
+    // Determine the `libclang` directory patterns.
+    let directories = if cfg!(target_os = "haiku") {
+        DIRECTORIES_HAIKU
+    } else if cfg!(any(target_os = "linux", target_os = "freebsd")) {
+        DIRECTORIES_LINUX
+    } else if cfg!(target_os = "macos") {
+        DIRECTORIES_MACOS
+    } else if cfg!(target_os = "windows") {
+        DIRECTORIES_WINDOWS
+    } else if cfg!(target_os = "illumos") {
+        DIRECTORIES_ILLUMOS
+    } else {
+        &[]
+    };
+
+    // Search the directories provided by the `libclang` directory patterns.
+    let mut options = MatchOptions::new();
+    options.case_sensitive = false;
+    options.require_literal_separator = true;
+    for directory in directories.iter().rev() {
+        if let Ok(directories) = glob::glob_with(directory, options) {
+            for directory in directories.filter_map(Result::ok).filter(|p| p.is_dir()) {
+                found.extend(search_directories(&directory, filenames));
+            }
+        }
+    }
+
+    found
+}
diff --git a/third_party/rust/clang-sys/build/dynamic.rs b/third_party/rust/clang-sys/build/dynamic.rs
new file mode 100644
index 0000000000..267ec81932
--- /dev/null
+++ b/third_party/rust/clang-sys/build/dynamic.rs
@@ -0,0 +1,262 @@
+// SPDX-License-Identifier: Apache-2.0
+
+use std::env;
+use std::fs::File;
+use std::io::{self, Error, ErrorKind, Read, Seek, SeekFrom};
+use std::path::{Path, PathBuf};
+
+use super::common;
+
+//================================================
+// Validation
+//================================================
+
+/// Extracts the ELF class from the ELF header in a shared library.
+fn parse_elf_header(path: &Path) -> io::Result<u8> {
+    let mut file = File::open(path)?;
+    let mut buffer = [0; 5];
+    file.read_exact(&mut buffer)?;
+    if buffer[..4] == [127, 69, 76, 70] {
+        Ok(buffer[4])
+    } else {
+        Err(Error::new(ErrorKind::InvalidData, "invalid ELF header"))
+    }
+}
+
+/// Extracts the magic number from the PE header in a shared library.
+fn parse_pe_header(path: &Path) -> io::Result<u16> {
+    let mut file = File::open(path)?;
+
+    // Extract the header offset.
+    let mut buffer = [0; 4];
+    let start = SeekFrom::Start(0x3C);
+    file.seek(start)?;
+    file.read_exact(&mut buffer)?;
+    let offset = i32::from_le_bytes(buffer);
+
+    // Check the validity of the header.
+    file.seek(SeekFrom::Start(offset as u64))?;
+    file.read_exact(&mut buffer)?;
+    if buffer != [80, 69, 0, 0] {
+        return Err(Error::new(ErrorKind::InvalidData, "invalid PE header"));
+    }
+
+    // Extract the magic number.
+    let mut buffer = [0; 2];
+    file.seek(SeekFrom::Current(20))?;
+    file.read_exact(&mut buffer)?;
+    Ok(u16::from_le_bytes(buffer))
+}
+
+/// Checks that a `libclang` shared library matches the target platform.
+fn validate_library(path: &Path) -> Result<(), String> {
+    if cfg!(any(target_os = "linux", target_os = "freebsd")) {
+        let class = parse_elf_header(path).map_err(|e| e.to_string())?;
+
+        if cfg!(target_pointer_width = "32") && class != 1 {
+            return Err("invalid ELF class (64-bit)".into());
+        }
+
+        if cfg!(target_pointer_width = "64") && class != 2 {
+            return Err("invalid ELF class (32-bit)".into());
+        }
+
+        Ok(())
+    } else if cfg!(target_os = "windows") {
+        let magic = parse_pe_header(path).map_err(|e| e.to_string())?;
+
+        if cfg!(target_pointer_width = "32") && magic != 267 {
+            return Err("invalid DLL (64-bit)".into());
+        }
+
+        if cfg!(target_pointer_width = "64") && magic != 523 {
+            return Err("invalid DLL (32-bit)".into());
+        }
+
+        Ok(())
+    } else {
+        Ok(())
+    }
+}
+
+//================================================
+// Searching
+//================================================
+
+/// Extracts the version components in a `libclang` shared library filename.
+fn parse_version(filename: &str) -> Vec<u32> {
+    let version = if let Some(version) = filename.strip_prefix("libclang.so.") {
+        version
+    } else if filename.starts_with("libclang-") {
+        &filename[9..filename.len() - 3]
+    } else {
+        return vec![];
+    };
+
+    version.split('.').map(|s| s.parse().unwrap_or(0)).collect()
+}
+
+/// Finds `libclang` shared libraries and returns the paths to, filenames of,
+/// and versions of those shared libraries.
+fn search_libclang_directories(runtime: bool) -> Result<Vec<(PathBuf, String, Vec<u32>)>, String> {
+    let mut files = vec![format!(
+        "{}clang{}",
+        env::consts::DLL_PREFIX,
+        env::consts::DLL_SUFFIX
+    )];
+
+    if cfg!(target_os = "linux") {
+        // Some Linux distributions don't create a `libclang.so` symlink, so we
+        // need to look for versioned files (e.g., `libclang-3.9.so`).
+        files.push("libclang-*.so".into());
+
+        // Some Linux distributions don't create a `libclang.so` symlink and
+        // don't have versioned files as described above, so we need to look for
+        // suffix versioned files (e.g., `libclang.so.1`). However, `ld` cannot
+        // link to these files, so this will only be included when linking at
+        // runtime.
+        if runtime {
+            files.push("libclang.so.*".into());
+            files.push("libclang-*.so.*".into());
+        }
+    }
+
+    if cfg!(any(
+        target_os = "freebsd",
+        target_os = "haiku",
+        target_os = "netbsd",
+        target_os = "openbsd",
+    )) {
+        // Some BSD distributions don't create a `libclang.so` symlink either,
+        // but use a different naming scheme for versioned files (e.g.,
+        // `libclang.so.7.0`).
+        files.push("libclang.so.*".into());
+    }
+
+    if cfg!(target_os = "windows") {
+        // The official LLVM build uses `libclang.dll` on Windows instead of
+        // `clang.dll`. However, unofficial builds such as MinGW use `clang.dll`.
+        files.push("libclang.dll".into());
+    }
+
+    // Find and validate `libclang` shared libraries and collect the versions.
+    let mut valid = vec![];
+    let mut invalid = vec![];
+    for (directory, filename) in common::search_libclang_directories(&files, "LIBCLANG_PATH") {
+        let path = directory.join(&filename);
+        match validate_library(&path) {
+            Ok(()) => {
+                let version = parse_version(&filename);
+                valid.push((directory, filename, version))
+            }
+            Err(message) => invalid.push(format!("({}: {})", path.display(), message)),
+        }
+    }
+
+    if !valid.is_empty() {
+        return Ok(valid);
+    }
+
+    let message = format!(
+        "couldn't find any valid shared libraries matching: [{}], set the \
+         `LIBCLANG_PATH` environment variable to a path where one of these files \
+         can be found (invalid: [{}])",
+        files
+            .iter()
+            .map(|f| format!("'{}'", f))
+            .collect::<Vec<_>>()
+            .join(", "),
+        invalid.join(", "),
+    );
+
+    Err(message)
+}
+
+/// Finds the "best" `libclang` shared library and returns the directory and
+/// filename of that library.
+pub fn find(runtime: bool) -> Result<(PathBuf, String), String> {
+    search_libclang_directories(runtime)?
+        .iter()
+        // We want to find the `libclang` shared library with the highest
+        // version number, hence `max_by_key` below.
+        //
+        // However, in the case where there are multiple such `libclang` shared
+        // libraries, we want to use the order in which they appeared in the
+        // list returned by `search_libclang_directories` as a tiebreaker since
+        // that function returns `libclang` shared libraries in descending order
+        // of preference by how they were found.
+        //
+        // `max_by_key`, perhaps surprisingly, returns the *last* item with the
+        // maximum key rather than the first which results in the opposite of
+        // the tiebreaking behavior we want. This is easily fixed by reversing
+        // the list first.
+        .rev()
+        .max_by_key(|f| &f.2)
+        .cloned()
+        .map(|(path, filename, _)| (path, filename))
+        .ok_or_else(|| "unreachable".into())
+}
+
+//================================================
+// Linking
+//================================================
+
+/// Finds and links to a `libclang` shared library.
+#[cfg(not(feature = "runtime"))]
+pub fn link() {
+    let cep = common::CommandErrorPrinter::default();
+
+    use std::fs;
+
+    let (directory, filename) = find(false).unwrap();
+    println!("cargo:rustc-link-search={}", directory.display());
+
+    if cfg!(all(target_os = "windows", target_env = "msvc")) {
+        // Find the `libclang` stub static library required for the MSVC
+        // toolchain.
+        let lib = if !directory.ends_with("bin") {
+            directory
+        } else {
+            directory.parent().unwrap().join("lib")
+        };
+
+        if lib.join("libclang.lib").exists() {
+            println!("cargo:rustc-link-search={}", lib.display());
+        } else if lib.join("libclang.dll.a").exists() {
+            // MSYS and MinGW use `libclang.dll.a` instead of `libclang.lib`.
+            // It is linkable with the MSVC linker, but Rust doesn't recognize
+            // the `.a` suffix, so we need to copy it with a different name.
+            //
+            // FIXME: Maybe we can just hardlink or symlink it?
+            let out = env::var("OUT_DIR").unwrap();
+            fs::copy(
+                lib.join("libclang.dll.a"),
+                Path::new(&out).join("libclang.lib"),
+            )
+            .unwrap();
+            println!("cargo:rustc-link-search=native={}", out);
+        } else {
+            panic!(
+                "using '{}', so 'libclang.lib' or 'libclang.dll.a' must be \
+                 available in {}",
+                filename,
+                lib.display(),
+            );
+        }
+
+        println!("cargo:rustc-link-lib=dylib=libclang");
+    } else {
+        let name = filename.trim_start_matches("lib");
+
+        // Strip extensions and trailing version numbers (e.g., the `.so.7.0` in
+        // `libclang.so.7.0`).
+        let name = match name.find(".dylib").or_else(|| name.find(".so")) {
+            Some(index) => &name[0..index],
+            None => name,
+        };
+
+        println!("cargo:rustc-link-lib=dylib={}", name);
+    }
+
+    cep.discard();
+}
diff --git a/third_party/rust/clang-sys/build/static.rs b/third_party/rust/clang-sys/build/static.rs
new file mode 100644
index 0000000000..79f4baf0c6
--- /dev/null
+++ b/third_party/rust/clang-sys/build/static.rs
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: Apache-2.0
+
+extern crate glob;
+
+use std::path::{Path, PathBuf};
+
+use glob::Pattern;
+
+use common;
+
+//================================================
+// Searching
+//================================================
+
+/// Clang static libraries required to link to `libclang` 3.5 and later.
+const CLANG_LIBRARIES: &[&str] = &[
+    "clang",
+    "clangAST",
+    "clangAnalysis",
+    "clangBasic",
+    "clangDriver",
+    "clangEdit",
+    "clangFrontend",
+    "clangIndex",
+    "clangLex",
+    "clangParse",
+    "clangRewrite",
+    "clangSema",
+    "clangSerialization",
+];
+
+/// Gets the name of an LLVM or Clang static library from a path.
+fn get_library_name(path: &Path) -> Option<String> {
+    path.file_stem().map(|p| {
+        let string = p.to_string_lossy();
+        if let Some(name) = string.strip_prefix("lib") {
+            name.to_owned()
+        } else {
+            string.to_string()
+        }
+    })
+}
+
+/// Gets the LLVM static libraries required to link to `libclang`.
+fn get_llvm_libraries() -> Vec<String> {
+    common::run_llvm_config(&["--libs"])
+        .unwrap()
+        .split_whitespace()
+        .filter_map(|p| {
+            // Depending on the version of `llvm-config` in use, listed
+            // libraries may be in one of two forms, a full path to the library
+            // or simply prefixed with `-l`.
+            if let Some(path) = p.strip_prefix("-l") {
+                Some(path.into())
+            } else {
+                get_library_name(Path::new(p))
+            }
+        })
+        .collect()
+}
+
+/// Gets the Clang static libraries required to link to `libclang`.
+fn get_clang_libraries<P: AsRef<Path>>(directory: P) -> Vec<String> {
+    // Escape the directory in case it contains characters that have special
+    // meaning in glob patterns (e.g., `[` or `]`).
+    let directory = Pattern::escape(directory.as_ref().to_str().unwrap());
+    let directory = Path::new(&directory);
+
+    let pattern = directory.join("libclang*.a").to_str().unwrap().to_owned();
+    if let Ok(libraries) = glob::glob(&pattern) {
+        libraries
+            .filter_map(|l| l.ok().and_then(|l| get_library_name(&l)))
+            .collect()
+    } else {
+        CLANG_LIBRARIES.iter().map(|l| (*l).to_string()).collect()
+    }
+}
+
+/// Finds a directory containing LLVM and Clang static libraries and returns the
+/// path to that directory.
+fn find() -> PathBuf {
+    let name = if cfg!(target_os = "windows") {
+        "libclang.lib"
+    } else {
+        "libclang.a"
+    };
+
+    let files = common::search_libclang_directories(&[name.into()], "LIBCLANG_STATIC_PATH");
+    if let Some((directory, _)) = files.into_iter().next() {
+        directory
+    } else {
+        panic!("could not find any static libraries");
+    }
+}
+
+//================================================
+// Linking
+//================================================
+
+/// Finds and links to `libclang` static libraries.
+pub fn link() {
+    let cep = common::CommandErrorPrinter::default();
+
+    let directory = find();
+
+    // Specify required Clang static libraries.
+    println!("cargo:rustc-link-search=native={}", directory.display());
+    for library in get_clang_libraries(directory) {
+        println!("cargo:rustc-link-lib=static={}", library);
+    }
+
+    // Determine the shared mode used by LLVM.
+    let mode = common::run_llvm_config(&["--shared-mode"]).map(|m| m.trim().to_owned());
+    let prefix = if mode.map_or(false, |m| m == "static") {
+        "static="
+    } else {
+        ""
+    };
+
+    // Specify required LLVM static libraries.
+    println!(
+        "cargo:rustc-link-search=native={}",
+        common::run_llvm_config(&["--libdir"]).unwrap().trim_end()
+    );
+    for library in get_llvm_libraries() {
+        println!("cargo:rustc-link-lib={}{}", prefix, library);
+    }
+
+    // Specify required system libraries.
+    // MSVC doesn't need this, as it tracks dependencies inside `.lib` files.
+    if cfg!(target_os = "freebsd") {
+        println!("cargo:rustc-flags=-l ffi -l ncursesw -l c++ -l z");
+    } else if cfg!(any(target_os = "haiku", target_os = "linux")) {
+        println!("cargo:rustc-flags=-l ffi -l ncursesw -l stdc++ -l z");
+    } else if cfg!(target_os = "macos") {
+        println!("cargo:rustc-flags=-l ffi -l ncurses -l c++ -l z");
+    }
+
+    cep.discard();
+}