check_dbi: Include extra opts in help output.

plugins/check_dbi.c

@@ -353,6 +353,11 @@ print_help (void)
 	print_usage ();
 
 	printf (UT_HELP_VRSN);
+/* include this conditionally to avoid 'zero-length printf format string'
+ * compiler warnings */
+#ifdef NP_EXTRA_OPTS
+	printf (UT_EXTRA_OPTS);
+#endif
 	printf ("\n");
 
 	printf (" %s\n", "-d, --driver=STRING");