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

[Jessica Clarke via cfe-commits]

jrtc27 wrote:

There seems to be some confusion here. As far as I can tell (and Gleb, please give explicit confirmation as to whether this is 100% accurate or not), no *code* has been copied (the variable names and formatting are different, it uses early return rather than variable assignment, and this even has the default case after the end of the switch rather than inside it), only the English text used for most of the error messages (possibly all but the arm64 PAC one?).

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