[Bug other/19180] Improve documentation on How to Add New GCC option

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19180

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Things have improved so much since this bug report was written and when I
confirmed it.  Devang left Apple back in 2012.