HDF5 on Cray systems

On cray systems (e.g. ARCHER or the Australian system Magnus) our configuration script fails to find HDF5. The reason is that these systems don't provide the users with the h5cc or h5pcc wrappers that our script is looking for.

Could we modify m4/ax_lib_hdf5 to receive an H5CC variable from the command line ? That would be similar to what we do for MPICC when not present. Or could we not use that set of macros all together ? It does not seem to do anything particularly useful apart from trying to retrieve version number and various configurations.