make-windows-release: support MSYS2 clang environments

make-windows-release: support MSYS2 clang environments

Update tools/make-windows-release to support the CLANG32 and CLANG64
MSYS2 environments, and update ci.yml to test them in GitHub Actions.

Also try to support CLANGARM64, though I have no way to test that yet.

Finally, make a couple more tweaks to make-windows-release:

- Run the configure script unless it's explicitly requested to be
  skipped, as the previous logic was too fragile.

- Default to no docs and no zip.