Skip building libclang_rt when WITHOUT_CLANG is used
As noted in bug 277096, when building a pkgbase repository using
WITHOUT_CROSS_COMPILER and WITHOUT_TOOLCHAIN (which sets WITHOUT_CLANG),
the following residual files are left over:
This is because the lib/libclang_rt directory is still descended into,
even if WITHOUT_CLANG is used. Fix it by not descending into the
libclang_rt directory in that case.