BUG: Unnecessary tools from niral_utilities are not compiled anymore

POLYDATATRANSFORM and POLYDATAMERGE need GenerateCLP to be built. Only SlicerExecutionModel_DIR is given to the derived Superbuild projects in the DTIPrep build system. The tools that need GenerateCLP could not find it. To avoid this compilation issue, we do not build these tools that are not needed by DTIPrep.