Before, -lz -ldl -lm -lrt would be turned into absolute paths. This doesn't work
for the Xeon Phi where we need to cross-compile. The Intel compiler
automatically adds the libraries with the correct architecture as long as -l
arguments are passed as is.
The FindHDF5.cmake packaged with CMake is broken in a number of respects. The HL
components don't work (debian has a patch in cmake-data). It's also impossible
to prefer a parallel installation if both h5fc and h5pfc appear on your
PATH. Finally, hdf5_hl is not included in the list of libraries needed for the
Fortran_HL component. A local version of FindHDF5 is used here which fixes all
these issues. This enables one to compile OpenMC with MPI + serial HDF5 if
needed by introducing the PHDF5 preprocessor flag.
