buildfix: We failed to build of CONFIG_MODULES is not set

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_main.c

@@ -3734,9 +3734,11 @@ const char *drbd_buildtag(void)
 	static char buildtag[38] = "\0uilt-in";
 
 	if (buildtag[0] == 0) {
+#ifdef CONFIG_MODULES
 		if (THIS_MODULE != NULL)
 			sprintf(buildtag, "srcversion: %-24s", THIS_MODULE->srcversion);
 		else
+#endif
 			buildtag[0] = 'b';
 	}