I have no idea why but ppc profile masks USE=clang globally. Not that it was ever intended global and eix is using it against all my shouting at the maintainer. Anyway, sys-devel/llvm now uses USE=clang to build clang and the mask hits that. And it sucks pretty much since sys-devel/clang requires llvm[clang], and is keyworded ~ppc. Please fix this mask ASAP.
Oh, sorry, it seems that the '~ppc' keyword I copied from llvm, not expecting the mask. Anyway, do you want to consider 're-keywording' it after it was integrated with llvm?
I dropped ppc keywords from clang/llvm.