Enable building libobjc with Intel CET

libobjc/
	* Makefile.in: Regenerate.
	* aclocal.m4: Likeiwse.
	* configure: Likewise.
	* configure.ac: Set CET_FLAGS. Update XCFLAGS.

From-SVN: r254904
diff --git a/libobjc/configure.ac b/libobjc/configure.ac
index c6d48f7..f24b5da 100644
--- a/libobjc/configure.ac
+++ b/libobjc/configure.ac
@@ -151,7 +151,12 @@
 esac
 AC_SUBST(extra_ldflags_libobjc)
 
+# Add CET specific flags if CET is enabled
+GCC_CET_FLAGS(CET_FLAGS)
+XCFLAGS="$XCFLAGS $CET_FLAGS"
+
 AC_SUBST(CFLAGS)
+AC_SUBST(XCFLAGS)
 
 AC_CHECK_TOOL(AS, as)
 AC_CHECK_TOOL(AR, ar)