[llvm] Reapply "[lit] Implement builtin umask (#94621)" (PR #155850)

[via llvm-commits]

dyung wrote:

This change has been causing Windows builders to be red for the last 6 hours or so. @boomanaiden154 if you do not have a fix in progress, can we either mark the test as unsupported on Windows as suggested by @tex3d, or revert the change while you investigate/fix?

https://lab.llvm.org/buildbot/#/builders/46/builds/22541

https://github.com/llvm/llvm-project/pull/155850