bug#25987: 25.2; support gcc fixit notes

[Andrea Corallo via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: David Malcolm <dmalcolm@redhat.com>
>> Cc: 25987@debbugs.gnu.org
>> Date: Wed, 14 Oct 2020 18:43:33 -0400
>> 
>> In his email, Andrea suggests outputting to a file.  How would 
>> that work?  It strikes me as making it difficult to associate the
>> output from stderr with that to the file, or would the output to the
>> file need to replace that from stderr (in which case what about lines
>> of output from "make"? or other build system messages, etc).
>
> I'm not sure how a separate file comes into this.  Aren't we talking
> about the "normal" GCC diagnostic output, just augmented by hints?
> That has the advantage that it is also human-readable, and could help
> the user make changes other than accepting the hints.

I explained this in my last mail on this thread, to make it short using
stderr can't work reliably for parallel builds.  Maybe we decide that's
good enought but has to be considered now as IMO it's a strong
limitation.

  Andrea