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

[Tom Stellard via llvm-commits]

tstellar wrote:

I re-worked the job now so that it automatically saves the build after 5 hours and 30 minutes and then continues it in a new job to avoid the GitHub timeouts.  This simplifies the workflow a lot, and let's us just run `ninja $check-targets` directly with no intermediate steps.   This job is now more or less equivalent to what is run on the buildkite builders.

I did some benchmarking and for full build of all the projects and running all the check targets (i.e. what happens if you make a change in llvm/) it takes 8 Hr 10 Minutes with no cache and 1Hr 45 Minutes with 100% cache usage.  There is a global sccache and also a local one for each PR.  I would expect in most cases, the first run for a PR will take the max time (8Hr 10M), and subsequent runs will take about 2 Hrs.  This is for PRs that touch llvm/  PRs that tough other directories will take less time to test.


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