crossdev either supports a profile which is built completely using clang or gcc -- it does not support a hybrid approach of building the optional gcc or clang compiler. This is needed because of many packages insist on clang/llvm like firefox, chromium, spidermonkey, dev-libs/libclc, dev-util/spirv-llvm-translator etc... Therefore there must be switches to build an optional gcc/llvm/clang compiler which will not be the system compiler, but will be available for use for use for the likes of above packages; otherwise building these packages with crossdev fails with error <archspec>-clang does not exist. Reproducible: Always
