on MacOS X add -lfreetype to the library list of --libs and --glibs.

When the ROOT binary directory is relocated the freetype lib linked to
libGraf is not found during linking, so we need to explicitely add it again.


git-svn-id: http://root.cern.ch/svn/root/trunk@10102 27541ba8-7e3a-0410-8455-c3a389f83636