Fixed Travis XCode builds.
Fixed Travis XCode builds.

The GCC Fortran compiler was not properly linked, thus CMake couldn't find it.

RWTH-ELP/PnMPI,RWTH-HPC/PnMPI,RWTH-HPC/PnMPI,RWTH-ELP/PnMPI,RWTH-ELP/PnMPI,RWTH-HPC/PnMPI