hdf5_msb

Fix `test/swmr_sparse_reader.c:118:77: error: cast from pointer
to integer of different size [-Werror=pointer-to-int-cast]` and
`test/snapshots-hdf5/current/test/swmr_sparse_reader.c:129:100:
error: cast from pointer to integer of different size
[-Werror=pointer-to-int-cast]`.