Add missing Python library

Distutils is usually included in Python 3.9 distributions.  For
the GitHub Windows Sesrver 2022, it isn't.  Trying adding setuptools,
which pip substitutes behind the scene for distutils.  Distutils is
deprecated and has been removed from later versions of Python.
When we upgrade our clang ources, we can follow what LLVM has done
for later versions of Python.

.github/workflows/check-clang-windows.yml

@@ -53,6 +53,8 @@ jobs:
         uses: actions/setup-python@v4
         with:
           python-version: '3.9'
+      - name: Add Python setuptools
+        run: pip3 install setuptools
       - name: Checkout Checked C Clang code
         uses: actions/checkout@v2
         with: