[Bug c/80638] -ansi suppresses -Wstringop-overflow for mempcpy

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80638

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>Calls to known library functions that overflow should be diagnosed regardless of -ansi.

No, because mempcpy is not included in the ISO standard.  Basically -ansi is
the same as doing -fstd=c11.