llvm,llvm-gcc-toolfile: update to work with GCC 4.8.1

Remove `-Wno-unused-local-typedefs' GCC option on LLVM/Clang, it's
not supported. Our (SLC{5,6}) triplet is x86_64-redhat-linux-gnu,
which is not available in Clang. Add it.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
Merge pull request #192 from davidlt/llvm-clang-gcc-4.8.1-support

llvm,llvm-gcc-toolfile: update to work with GCC 4.8.1