Add Freetype to ohroot dependencies.
ROOT's libGraf.so library depends on the freetype library. It seems so far we have picked up the system version, not the one from LCG. The problem has only shown up in a cross-compilation environment where the freetype-devel RPM was missing from the installation on the host.
The CentOS 7 and LCG versions for freetype were 2.8 and 2.10 rsp., so probably close enough to work.
@kolos , can you merge. At run-time we were already setting up the proper LD_LIBRARY_PATH, so that should be ok.