Auto merge of #149601 - mati865:no-msys2-take2, r=<try>

Stop adding MSYS2 to PATH, take 2

try-job: dist-i686-mingw

Author: rust-bors[bot]

src/ci/scripts/install-mingw.sh

@@ -66,5 +66,8 @@ if isWindows && isKnownToBeMingwBuild; then
             ;;
     esac
 
+    # Prevent adding /mingw64/bin Git for Windows to PATH
+    echo "MSYSTEM=" >> "$GITHUB_ENV"
+
     ciCommandAddPath "$(cygpath -m "$(pwd)/${mingw_dir}/bin")"
 fi