Fix CMake: HDF5 Libs are PUBLIC

[ax3l]

We do not yet use FindHDF5.cmake CMake targets and thus need to ensure the libs are propagated properly (they are not consumed necessarily as private)

First seen when building with -Wl,--disable-new-dtags for RPATH over newer RUNPATH.

FindHDF5.cmake introduced targets in 3.19 but changed them again in 3.20+:

• https://cmake.org/cmake/help/v3.19/module/FindHDF5.html
• https://cmake.org/cmake/help/v3.20/module/FindHDF5.html