Fix test to pass when the directory name has lld in it.

CHECK-LABEL assumes that there is only one occurrence of the match.

The output looks like:

clang version 3.8.0 (trunk 247999)
....
/path/to/build/dir/bin/clang-3.8 ....

If the path contains lld, the second CHECK-LABEL matches it and we fail since
there is no -cc1as between clang and lld.

llvm-svn: 248029