Use C11's noreturn

Also define noreturn w/o <stdnoreturn.h> and move it to macro.h instead
of in the testsuite.

Based on similar commit on systemd by Shawn Landden
<[email protected]>.
diff --git a/testsuite/test-depmod.c b/testsuite/test-depmod.c
index 0ea8982..e21b4f0 100644
--- a/testsuite/test-depmod.c
+++ b/testsuite/test-depmod.c
@@ -29,7 +29,7 @@
 #define MODULES_ORDER_UNAME "3.5.4-1-ARCH"
 #define MODULES_ORDER_ROOTFS TESTSUITE_ROOTFS "test-depmod/modules-order-compressed"
 #define MODULES_ORDER_LIB_MODULES MODULES_ORDER_ROOTFS "/lib/modules/" MODULES_ORDER_UNAME
-static __noreturn int depmod_modules_order_for_compressed(const struct test *t)
+static noreturn int depmod_modules_order_for_compressed(const struct test *t)
 {
 	const char *progname = ABS_TOP_BUILDDIR "/tools/depmod";
 	const char *const args[] = {