[Bug bootstrap/97163] Build error with -mcpu=power9 on ppc64

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97163

--- Comment #7 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Ah.

Is there no better way to detect GCC impostors?  Oh well.

Since we require 4.5 as bootstrap compiler, this makes no difference
at all for compilers that truthfully claim to be GCC, so it has my
blessing if you want that :-)

Thanks!