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

[Jessica Clarke via cfe-commits]

jrtc27 wrote:

> > I deliberately didn't talk about that in this part of my message because it's not relevant; adding code does not affect whether the rest of the code is a license violation.
> 
> Yes, but it is also a sort of evidence that I didn't just blindly copy the nongnu code.

Not really. If you'd copied the nongnu code verbatim and added a single `case UNW_ECROSSRASIGNING: cp = "..."; break;` line (well, with ifdefs) then it wouldn't have done anything to help your case. What matters is everything else.

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