Comment # 39 on bug 111077 from Matt Turner

(In reply to roland@rptd.ch from comment #38)
> Could it be that your patch is not for version "mesa-19.0.8" as I'm using?
> (newer ones are keyworded)

Perhaps try 19.2.0_rc3. That's much closer to master.

Whatever the case, if the patch doesn't apply to 19.0.8 and portage tried (and
as a result failed) to apply it, it would give an error and stop.