[Bug target/101865] _ARCH_PWR8 is not defined when using -mcpu=power8

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101865

--- Comment #21 from Peter Bergner <bergner at gcc dot gnu.org> ---
Fixed on trunk.  I'll let it burn-in there for a bit before backporting to the
release branches.