PR91349, powerpc64*-*-freebsd* defines _GNU_SOURCE

rev 266496 (git ab6b1bb456) undefined some macros in rs6000/freebsd.h
but missed doing the same in rs6000/freebsd64.h.

	PR target/91349
	* config/rs6000/freebsd64.h (CPLUSPLUS_CPP_SPEC),
	(LINK_GCC_C_SEQUENCE_SPEC): Undef.

From-SVN: r274105

gcc/ChangeLog

+2019-08-05  Alan Modra  <amodra@gmail.com>
+
+	PR target/91349
+	* config/rs6000/freebsd64.h (CPLUSPLUS_CPP_SPEC),
+	(LINK_GCC_C_SEQUENCE_SPEC): Undef.
+
 2019-08-04  Gerald Pfeifer  <gerald@pfeifer.com>
 
 	* doc/install.texi (Prerequisites): Remove reference to Tcl 8.6

gcc/config/rs6000/freebsd64.h

@@ -17,6 +17,10 @@
    along with GCC; see the file COPYING3.  If not see
    <http://www.gnu.org/licenses/>.  */
 
+/* Undef gnu-user.h macros we don't want.  */
+#undef CPLUSPLUS_CPP_SPEC
+#undef LINK_GCC_C_SEQUENCE_SPEC
+
 /* Override the defaults, which exist to force the proper definition.  */
 
 #ifdef IN_LIBGCC2