[clang] [llvm] [LLVM][Clang][Cygwin] Fix building Clang for Cygwin (PR #134494)

[Mateusz Mikuła via cfe-commits]

mati865 wrote:

Okay, you were right.
Keeping this in a single description hurts readability a lot.

So I have opened a series of smaller PRs:
https://github.com/llvm/llvm-project/pull/138117
https://github.com/llvm/llvm-project/pull/138118
https://github.com/llvm/llvm-project/pull/138119
https://github.com/llvm/llvm-project/pull/138120

This branch is equal to the other ones (once they are merged together), so we can go either way.
I think you can publish them from drafts once you are happy with them. You can also mention me on GH, so I get the notification instantly and publish them.

https://github.com/llvm/llvm-project/pull/134494