Update autotest tests to use make -j where possible.

client/site_tests/platform_MiniJailReadOnlyFS/platform_MiniJailReadOnlyFS.py

 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging
 import os
 import re
 
 from autotest_lib.client.bin import test
 from autotest_lib.client.common_lib import error, utils
 
 class platform_MiniJailReadOnlyFS(test.test):
     version = 1
     preserve_srcdir = True
 
     def setup(self):
         os.chdir(self.srcdir)
-        utils.system('make clean')
-        utils.system('make all')
+        utils.make('clean')
+        utils.make('all')
 
 
     def __run_cmd(self, cmd):
         result = utils.system_output(cmd, retain_output=True,
                                      ignore_status=True)
         return result
 
 
     def run_once(self):
         # Check that --add-readonly-mounts works
         check_cmd = (os.path.join(self.bindir, 'platform_MiniJailReadOnlyFS') +
               ' --procIsReadOnly')
         cmd = ('/sbin/minijail --add-read-only-mounts -- ' + check_cmd)
         result = self.__run_cmd(cmd)
         succeed_pattern = re.compile(r"SUCCEED: (.+)")
         success = succeed_pattern.findall(result)
         if len(success) == 0:
           raise error.TestFail('The /proc directory is not read-only')