message: Added C compiler spec.
diff: set(RAJA_COMPILER "RAJA_COMPILER_GNU" CACHE STRING "")
  set(CMAKE_CXX_COMPILER "/usr/local/tools/compilers/ibm/mpicxx-4.7.2b" CACHE PATH "")
  +set(CMAKE_C_COMPILER "/usr/local/tools/compilers/ibm/mpicc-4.7.2b" CACHE PATH "")
  set(TEST_DRIVER srun CACHE STRING "use slurm to launch on BGQ")
  