Upgrade CMP0042 to NEW
Upgrade CMP0042 to NEW

If PnMPI is not installed in a system's library path, it needs to be
linked with '@rpath' to be relocatable. CMP0042 will take care of it.

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