[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 #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
If you had used __builtin_mempcpy you would have got the warning.