workflows/llvm-project-tests: Workaround an issue with lldb builds on Windows

[tstellar]

Summary

For some reason cmake started selecting a 32-bit version of python on
Windows instead of the 64-bit version when building windows. Explicitly
setting the default python to 3.10 fixes this problem.

[thieta]

LGTM!

.github/workflows/llvm-project-tests.yml

strategy:
           # https://github.com/actions/virtual-environments/issues/5900
           - macOS-11
     steps:
       - name: Setup Windows
         if: startsWith(matrix.os, 'windows')
         uses: llvm/actions/setup-windows@main
         with:
           arch: amd64
+      # On Windows, starting with win19/20220814.1, cmake choose the 32-bit
+      # python3.10.6 libraries instead of the 64-bit libraries when building
+      # lldb.  Using this setup-python action to make 3.10 the default
+      # python fixes this.
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
       - name: Install Ninja
         uses: llvm/actions/install-ninja@main
       # actions/checkout deletes any existing files in the new git directory,
       # so this needs to either run before ccache-action or it has to use
       # clean: false.
       - uses: actions/checkout@v3
         with:
           fetch-depth: 250