Removed CMAKE_CURRENT_LIST_DIR (it's too new)
Removed CMAKE_CURRENT_LIST_DIR (it's too new)

Changed this to an absolute reference to the PnMPI CMake include directory, rather than
relying on too-recent CMake features.

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