[libunwind] libunwind: Implement the unw_strerror function for better nongnu libunwind compatibility (PR #160887)

[Gleb Popov via cfe-commits]

arrowd wrote:

All right, and once again, why did you close the PR? Is it rejected? I shouldn't try to fix raised comments and improve it?

https://github.com/llvm/llvm-project/pull/160887