[Bug c++/78283] -Wc++1z-compat warning is sticky

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78283

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #1)
> Created attachment 40011 [details]
> gcc7-pr78283.patch
> 
> Untested fix.

OK.