Put back missing BuildFlatFiles() call.
Put back missing BuildFlatFiles() call.

It was done in the later startup passes, which were removed. Add the call
to where it is in the upstream.

Fix compiler warning about unused variable in the passing.

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