Fixed compiler warnings

extra/mariabackup/xtrabackup.cc

@@ -6445,7 +6445,6 @@ int main(int argc, char **argv)
 {
 	char **client_defaults, **server_defaults;
 	char cwd[FN_REFLEN];
-	static char INNOBACKUPEX_EXE[]= "innobackupex";
 	if (argc > 1 && (strcmp(argv[1], "--innobackupex") == 0))
 	{
 		argv++;

sql/item_func.cc

@@ -3959,7 +3959,7 @@ longlong Item_master_gtid_wait::val_int()
 {
   DBUG_ASSERT(fixed == 1);
   longlong result= 0;
-  String *gtid_pos = args[0]->val_str(&value);
+  String *gtid_pos __attribute__((unused)) = args[0]->val_str(&value);
 
   if (args[0]->null_value)
   {

sql/slave.cc

@@ -3611,7 +3611,9 @@ int
 apply_event_and_update_pos_for_parallel(Log_event* ev, THD* thd,
                                         rpl_group_info *rgi)
 {
+#ifndef DBUG_OFF
   Relay_log_info* rli= rgi->rli;
+#endif
   mysql_mutex_assert_not_owner(&rli->data_lock);
   int reason= apply_event_and_update_pos_setup(ev, thd, rgi);
   /*