[PATCH] [OPENMP] Replace libgomp by libiomp5 in driver

[Dmitri Gribenko]

  We just used to link in libgomp for compatibility with gcc, is this correct?  (For example, some object files could be compiled with GCC with OpenMP, while the rest of the program could be compiled with clang and linked with 'clang -fopenmp'.)

  If it is so, I think the change is good, the users can get the previous behavior by specifying the required libraries manually.

http://llvm-reviews.chandlerc.com/D2841