Enable building libatomic with Intel CET

libatomic/
	* configure.ac: Set CET_FLAGS, update XCFLAGS.
	* acinclude.m4: Add cet.m4 and enable.m4.
	* configure: Regenerate.
	* Makefile.in: Likewise.
	* testsuite/Makefile.in: Likewise.

From-SVN: r254893
diff --git a/libatomic/configure.ac b/libatomic/configure.ac
index 023f172..bf7315e 100644
--- a/libatomic/configure.ac
+++ b/libatomic/configure.ac
@@ -238,6 +238,10 @@
   XCFLAGS="$XCFLAGS -Wall -Werror"
 fi
 
+# Add CET specific flags if CET is enabled
+GCC_CET_FLAGS(CET_FLAGS)
+XCFLAGS="$XCFLAGS $CET_FLAGS"
+
 XCFLAGS="$XCFLAGS $XPCFLAGS"
 
 AC_SUBST(config_path)