add missing halp, for r2 -x

binr/radare2/radare2.c

@@ -142,6 +142,7 @@ static int main_help(int line) {
 		" -u           set bin.filter=false to get raw sym/sec/cls names\n"
 		" -v, -V       show radare2 version (-V show lib versions)\n"
 		" -w           open file in write mode\n"
+		" -x           open file with exec-flag (for analysis mostly)\n"
 		" -z, -zz      do not load strings or load them even in raw\n");
 	}
 	if (line == 2) {