When using system HDF5, xdmf3 was failing to build since it was
attempting to link against -lvtkhdf5. The issue was coming from the use
of vtkxdmf3_LINK_DEPENDS. That piece of code seems a little out of place
since no other third party module does that. The CMakeLists.txt already
handled all link dependencies properly, hence this was not necessary and
causing the issue.