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

[Paul T Robinson via llvm-commits]

pogo59 wrote:

Thanks for the git tip!

At this point, I'm confident that `lit` will work correctly on Windows, and it's a matter of making the tests play nice in that environment.

Now, `ninja check-lit` already has another 5 failures in my Windows environment, so I'd be okay with it if you want to file an issue (assign to me) to fix up this case too. I'm annoyed enough at the situation to devote some time to tidying up the check-lit failures, and once those are actually working I can file an issue to get `check-lit` added to the bots.

Or, if you'd rather, we can work together on this test now.

https://github.com/llvm/llvm-project/pull/94621