regent: Disable GASNet by default on macOS.
regent: Disable GASNet by default on macOS.

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