Use --system for unix command's

mysql-test/t/mysqldump.test

@@ -647,7 +647,7 @@ select '------ Testing with illegal table names ------' as test_sequence ;
 --exec $MYSQL_DUMP --compact --skip-comments mysqldump_test_db  "\\t1" 2>&1
  
 --error 6
---exec $MYSQL_DUMP --compact --skip-comments mysqldump_test_db  "\\\\t1" 2>&1
+--exec $MYSQL_DUMP --compact --skip-comments mysqldump_test_db  "\\\\\\t1" 2>&1
 
 --error 6
 --exec $MYSQL_DUMP --compact --skip-comments mysqldump_test_db  "t\1" 2>&1
@@ -830,11 +830,11 @@ DROP TABLE t1, t2;
 # Bugs #9136, #12917: problems with --defaults-extra-file option
 #
 
---exec echo "[mysqltest1]" > $MYSQL_TEST_DIR/var/tmp/tmp.cnf
---exec echo "port=1234" >> $MYSQL_TEST_DIR/var/tmp/tmp.cnf
+--system echo "[mysqltest1]" > $MYSQL_TEST_DIR/var/tmp/tmp.cnf
+--system echo "port=1234" >> $MYSQL_TEST_DIR/var/tmp/tmp.cnf
 --exec $MYSQL_MY_PRINT_DEFAULTS -c $MYSQL_TEST_DIR/var/tmp/tmp.cnf mysqltest1
 --exec $MYSQL_MY_PRINT_DEFAULTS -e $MYSQL_TEST_DIR/var/tmp/tmp.cnf mysqltest1 mysqltest1
---exec rm $MYSQL_TEST_DIR/var/tmp/tmp.cnf
+--system rm $MYSQL_TEST_DIR/var/tmp/tmp.cnf
 
 #
 # Test of fix to BUG 12597