[Bug c/124699] [13 only] Expression using __builtin_ffsll() may not be considered constant

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124699

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note only 13 is still active branch. Though there is only one release left from
it. Will be in about a month time. I am not sure if this will be fixed there.