Remove commented-out block of macOS makefile stuff.
Remove commented-out block of macOS makefile stuff.

I don't understand what all this was about, but people have compiled GPDB
successfully after the merge commit, where this was commented out, so
apparently it's not needed.

jmcatamney/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,xinzweb/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,lisakowen/gpdb,lisakowen/gpdb,ashwinstar/gpdb,50wu/gpdb,adam8157/gpdb,50wu/gpdb,lisakowen/gpdb,jmcatamney/gpdb,adam8157/gpdb,greenplum-db/gpdb,adam8157/gpdb,xinzweb/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,ashwinstar/gpdb,xinzweb/gpdb,adam8157/gpdb,50wu/gpdb,ashwinstar/gpdb,adam8157/gpdb,50wu/gpdb,lisakowen/gpdb,jmcatamney/gpdb,adam8157/gpdb,lisakowen/gpdb,50wu/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,50wu/gpdb,jmcatamney/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,lisakowen/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,adam8157/gpdb,xinzweb/gpdb,ashwinstar/gpdb,lisakowen/gpdb,greenplum-db/gpdb,50wu/gpdb