cmake: use the native HDF5 finder
This is part of series of PRs from Debian fixes (see https://anonscm.debian.org/cgit/debian-science/packages/gmsh.git/tree/debian/patches).
This patch makes sure that Gmsh uses CMake's own HDF5 finder via find_package(HDF5)
. It handles all cases of system HDF5 installations and can be configured accordingly (see /usr/share/cmake-3.9/Modules/FindHDF5.cmake
).