regent: can control the building of GASNET & HDF through USE_* env vars
regent: can control the building of GASNET & HDF through USE_* env vars

StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion