[llvm] [workflows] Port buildkite Windows config to GitHub actions (PR #82093)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> Shall we actually setup a proof of concept custom GCP Windows runner? Then we can just invite Google to actually migrate the buildkite runners to GitHub instead. I seem to recall Microsoft ready to provide some machine as well? (@AaronBallman knows maybe?).
Having more beefy machines (+ having sizable local persistent sccache as well). may just be what we need here.

Migrating the current infrastructure over to Github Actions is already on Google's roadmap (@gchatelet @Keenuts), but not in the short-term from what I understand.

I remember Aaron saying that Intel would be willing to provide machines, but if I'm remembering that correctly, it was just hardware that would still need to be plugged in somewhere, and I don't believe anyone is willing to take in hardware and run it currently.

https://github.com/llvm/llvm-project/pull/82093