#2235: ExternalLibraries/HDF5 fails to correctly set up include paths when auto-detecting library

Comment (by Roland Haas):

Note, in response to https://bitbucket.org/einsteintoolkit/tickets/issues/2235/externallibraries-hdf5-fails-to-correctly#comment-51201211, that the issue does not only occur when one would build HDF5 using ExternalLibraries (in fact if one was to build it within the ExternalLibrary then the issue would not show up, it only shows up when using the HomeBrew provided libhdf5).