[Bug driver/123558] [13/14/15/16 Regression] -Fdir option should be darwin only

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123558

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Plus being in c-family/c.opt only seems odd.
It should have been in both common.opt for the driver handling and
c-family/c.opt.

Maybe there is a way to get darwin.opt to override generic handling where we do
an error message ...