[llvm] [Github][CI] Add Windows Premerge Job for Testing (PR #122661)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

Example of a successful run: https://github.com/llvm/llvm-project/actions/runs/12962666810/job/36159396020?pr=122661

https://github.com/llvm/llvm-project/pull/122661