Switch the driver back to always using clang-cc by default (for C++, and

regardless of the architecture).
 - This is a good default for development & testing; for example without this
   any tests using 'clang' in the test suite will fail on PowerPC, since the
   driver will avoid using clang.

 - We don't want to actually ship something built this way, but that should be
   handled via some sort of configuration file.

llvm-svn: 76886