When issuing 'emerge -av xorg-x11' I got the following:

all ebuilds that could satisfy x11-apps/luit have been masked
x11-apps/luit-1.1.1::xorg-kit masked by invalid DEPEND:USE
flag 'ppc-aix' referenced in conditional 'ppc-aix?' is not in IUSE

I tried to unmask the package via package.mask by either adding or removing the ppc-aix flag to luit, but neither seems to do anything.
the arch is piledriver, with an gfxcard-amdgpu mix-in (radeon HD7970 video card) if that matters