Update d3d12 script to support mesa 23.1.9-1

[adamscott]

This PR adds:

• a check to make sure the script is not run on platforms other than Windows
• an argparser in order to support --mesa-build (msvc, llvm, or gcc)
• support for download the desired builds of mesa 23.1.9-1 (as the downloads changed, but the script didn't)

[adamscott]

@bruvzg I renamed the option to --compiler (instead of --mesa-build)