/usr/lib/x86_64-linux-gnu/libhdf5_serialhl_fortran.so.100 is in libhdf5-100 1.10.0-patch1+docs-3+deb9u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libhdf5_serialhl_fortran.so.100.0.0