CI tests do not detect `clang_cl` tests that would break on non-Windows test hosts

[sivadeilra]

See this thread: #145565 (comment)

This PR added new llvm-lit tests for clang-cl. The PR CI jobs were green, but after merging, it was found that this broke Solaris buildbot.

This issue is for finding a way to detect this problem during PR CI jobs, so that breaks can be found before merging.

[boomanaiden154]

We run the default check targets on both Linux and Windows in the premerge CI. I do not think anyone is willing to invest sufficient resources or is there sufficient interest from the community to look at standing up premerge CI for a less common OS like Solaris.

If this could be caught on Linux, then the test just needs to run on Linux under check-clang.

[sivadeilra]

Right, I'm not suggesting that Solaris itself be part of the pre-merge CI checks. But if there was a way to catch this particular kind of break on Linux, then it would save some hassle.