[llvm] [Support] Add WrappedError class (PR #191706)

[via llvm-commits]

aokblast wrote:

> I feel this is a one-consumer hack dressed up as a general primitive... I think we should close this one, focus on 191708, and if we find a generalizable pattern, reopen this PR.
> 
> For 191708, we can introduce this helper
> 
> ```c++
>   void ObjDumper::reportUniqueWarning(const Twine &Key,
>                                       const Twine &Message) const {
>     SmallString<128> KeyStorage;
>     if (!Warnings.insert(Key.toStringRef(KeyStorage).str()).second)
>       return;                                  // duplicate — drop it
>     reportWarning(createStringError(object::object_error::parse_failed, Message),
>                   ObjName);
>   }
> ```

This helper is not enough, readelf pass WarnHandler to functions in Support/ELF.h since it also want to catch and deduplicate the error from ELF class. I think it would be better if we have some wrapped error stuff instead of modifying WarnHandler to accept two strings. See: https://github.com/llvm/llvm-project/pull/191707

https://github.com/llvm/llvm-project/pull/191706