[Bug middle-end/82479] missing popcount builtin detection

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82479

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note __builtin_popcount is correctly done for aarch64 already (I/Naveen added
it for GCC 7).