[Bug target/93811] __builtin___clear_cache() is a noop on powerpc (which is incorrect)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93811

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Mono's implementation seems like the best so far:
https://github.com/mono/mono/blob/main/mono/mini/mini-ppc.c#L759-L795