[libunwind] libunwind: Remove OS requirements from tests to make them run on more OSes (PR #167642)

[Martin Storsjö via cfe-commits]

mstorsjo wrote:

> I have just re-reviewed my changes once more to be sure. Can we merge this?

Feel free to. Or do you need someone else to merge it for you?

https://github.com/llvm/llvm-project/pull/167642