The linker flags for setting the compatibility and current versions of
libraries on Darwin are set for the supported Fortran compilers.
Set CMAKE_Fortran_CREATE_SHARED_LIBRARY for the NAG Fortran compiler to
have no space after <SONAME_FLAG> so the NAG compiler can parse the
argument correctly.
The commit "Split GNU compiler information files" broke the settings of
CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS
CMAKE_SHARED_MODULE_CREATE_${lang}_FLAGS
and started using just "-shared" for them. This worked when tested on newer
Mac machines, but older ones really need "-dynamiclib" and "-bundle" (which are
the documented flags anyway).