our cargo doesn't know about the 'output' part yet, this patch can be dropped
with cargo >= 0.64

diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 0ab4824ac0a..76c476f449b 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -1241,9 +1241,9 @@
         // complete list of features, so for that reason we don't enable checking of
         // features for std crates.
         cargo.arg(if mode != Mode::Std {
-            "-Zcheck-cfg=names,values,output,features"
+            "-Zcheck-cfg=names,values,features"
         } else {
-            "-Zcheck-cfg=names,values,output"
+            "-Zcheck-cfg=names,values"
         });
 
         // Add extra cfg not defined in/by rustc