Prevent Git4Win from prepending to PATH

Author: ChrisDenton

src/ci/scripts/install-mingw.sh

@@ -32,6 +32,11 @@ if isWindows && isKnownToBeMingwBuild; then
             ;;
     esac
 
+    # Stop Git4Win from prepending /msys64/bin to PATH.
+    msys2Path="c:/msys64"
+    mkdir -p "${msys2Path}/home/${USERNAME}"
+    ciCommandAddPath "${msys2Path}/usr/bin"
+
     mingw_dir="mingw${bits}"
 
     curl -o mingw.7z "${MIRRORS_BASE}/${mingw_archive}"