spack/var/spack/mock_configs/site_spackconfig/compilers.yaml

compilers:
  all:
    clang@3.3:
      cc: /path/to/clang
      cxx: /path/to/clang++
      f77: None
      fc: None
      modules: None
    gcc@4.5.0:
      cc: /path/to/gcc
      cxx: /path/to/g++
      f77: /path/to/gfortran
      fc: /path/to/gfortran
      modules: None
    gcc@5.2.0:
        cc: cc
        cxx: CC
        f77: ftn
        fc: ftn
        modules:
        - PrgEnv-gnu
        - gcc/5.2.0