Cygwin perl calls /bin/sh which can't resolve to .exe

Also Cygwin perl has $Config{osname} different from MSWin32, and why even check that?

--- postgresql/src/tools/msvc/build.pl.orig	2021-01-19 17:36:09.801463500 +0100
+++ postgresql/src/tools/msvc/build.pl	2021-01-19 17:36:20.426821300 +0100
@@ -55,13 +55,13 @@
 if ($buildwhat)
 {
 	system(
-		"msbuild $buildwhat.vcxproj /verbosity:normal $msbflags /p:Configuration=$bconf"
+		"msbuild.exe $buildwhat.vcxproj /verbosity:normal $msbflags /p:Configuration=$bconf"
 	);
 }
 else
 {
 	system(
-		"msbuild pgsql.sln /verbosity:normal $msbflags /p:Configuration=$bconf"
+		"msbuild.exe pgsql.sln /verbosity:normal $msbflags /p:Configuration=$bconf"
 	);
 }
 
--- postgresql/src/tools/msvc/Project.pm.orig	2021-01-19 17:59:18.799237700 +0100
+++ postgresql/src/tools/msvc/Project.pm	2021-01-19 17:59:48.487711700 +0100
@@ -22,7 +22,7 @@
 	my $self = {
 		name                  => $name,
 		type                  => $type,
-		guid                  => $^O eq "MSWin32" ? Win32::GuidGen() : 'FAKE',
+		guid                  => Win32::GuidGen(),
 		files                 => {},
 		references            => [],
 		libraries             => [],
--- postgresql/src/tools/msvc/Solution.pm.orig	2021-01-19 18:03:04.594229100 +0100
+++ postgresql/src/tools/msvc/Solution.pm	2021-01-19 18:04:13.677610100 +0100
@@ -59,7 +59,7 @@
 {
 	my $self = shift;
 
-	if ($^O eq "MSWin32")
+	if (1) #($^O eq "MSWin32")
 	{
 		# Examine CL help output to determine if we are in 32 or 64-bit mode.
 		my $output = `cl /? 2>&1`;
@@ -1100,7 +1100,7 @@
 		}
 		if ($fld ne "")
 		{
-			$flduid{$fld} = $^O eq "MSWin32" ? Win32::GuidGen() : 'FAKE';
+			$flduid{$fld} = Win32::GuidGen();
 			print $sln <<EOF;
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "$fld", "$fld", "$flduid{$fld}"
 EndProject
--- postgresql/src/tools/msvc/VSObjectFactory.pm.orig	2021-01-19 18:06:42.633421700 +0100
+++ postgresql/src/tools/msvc/VSObjectFactory.pm	2021-01-19 18:06:28.663523200 +0100
@@ -131,7 +131,7 @@
 
 sub DetermineVisualStudioVersion
 {
-	if ($^O eq "MSWin32")
+	if (1) # ($^O eq "MSWin32")
 	{
 		# To determine version of Visual Studio we use nmake as it has
 		# existed for a long time and still exists in current Visual
--- postgresql/src/tools/msvc/Mkvcbuild.pm.orig	2021-01-19 18:23:59.830153900 +0100
+++ postgresql/src/tools/msvc/Mkvcbuild.pm	2021-01-19 18:24:04.095411300 +0100
@@ -9,7 +9,7 @@
 use warnings;
 
 use Carp;
-use if ($^O eq "MSWin32"), 'Win32';
+use Win32;
 use Project;
 use Solution;
 use Cwd;
--- postgresql/src/tools/msvc/Solution.pm.orig	2021-01-19 20:27:21.366237600 +0100
+++ postgresql/src/tools/msvc/Solution.pm	2021-01-19 20:28:17.773662900 +0100
@@ -126,7 +126,8 @@
 	# openssl.exe is in the specified directory.
 	# Quote the .exe name in case it has spaces
 	my $opensslcmd =
-	  qq("$self->{options}->{openssl}\\bin\\openssl.exe" version 2>&1);
+	  qq("$self->{options}->{openssl}\\apps\\openssl.exe" version 2>&1);
+ print "$opensslcmd";
 	my $sslout = `$opensslcmd`;
 
 	$? >> 8 == 0
@@ -967,8 +967,8 @@
 				# On both Win32 and Win64 the same library
 				# names are used without a debugging context.
 				$dbgsuffix     = 0;
-				$libsslpath    = '\lib\libssl.lib';
-				$libcryptopath = '\lib\libcrypto.lib';
+				$libsslpath    = '\libssl.lib';
+				$libcryptopath = '\libcrypto.lib';
 			}
 
 			$proj->AddLibrary($self->{options}->{openssl} . $libsslpath,
@@ -993,9 +993,9 @@
 				# to be here, so don't ask for it in last
 				# parameter.
 				$proj->AddLibrary(
-					$self->{options}->{openssl} . '\lib\ssleay32.lib', 0);
+					$self->{options}->{openssl} . '\ssleay32.lib', 0);
 				$proj->AddLibrary(
-					$self->{options}->{openssl} . '\lib\libeay32.lib', 0);
+					$self->{options}->{openssl} . '\libeay32.lib', 0);
 			}
 		}
 	}