Revert "Have dtrace depend on object files directly, not objfiles.txt"
Revert "Have dtrace depend on object files directly, not objfiles.txt"

This reverts commit 73537828537239923a0f827a92b20502a3efa52d.  Per
report from Tom Lane, this breaks parallel builds.

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