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

[Vlad Serebrennikov via llvm-commits]

Endilll wrote:

Thank you for working on this Tom!

> I do have very strong concerns about this: it does not seem acceptable to me to make steps in a direction where we're reduce the previous support and make it seems that there are two classes of support in the project between subprojects.

It has been mentioned multiple times that there are technical limitations that need to be taken into account. I'd prefer myself if powerful Windows machines on BuildKite that have capacity for every project have been working properly, but it's not the case.

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