graphics/mesa-devel: fix build on powerpc64*

Allow anv on powerpc64* in OPTIONS_EXCLUDE to properly pass -Dintel-rt=disabled:
meson.build:291:3: ERROR: Feature intel-rt cannot be enabled: Intel Ray Tracing is only supported on x86_64

Additionaly, add an uncommitted patch from MR for powerpc64le.

(cherry picked from commit ed9185fb6e561ee48614189cadafc552db68f175)