ninja: use clang by default on Mac, matching recent Xcodes

pylib/gyp/generator/ninja.py

 # Copyright (c) 2013 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import copy
 import hashlib
 import json
 import multiprocessing
 import os.path
 import re
@@ skipping 1661 matching lines @@
   #   to cc/cxx.
   if flavor == 'win':
     # Overridden by local arch choice in the use_deps case.
     # Chromium's ffmpeg c99conv.py currently looks for a 'cc =' line in
     # build.ninja so needs something valid here. http://crbug.com/233985
     cc = 'cl.exe'
     cxx = 'cl.exe'
     ld = 'link.exe'
     ld_host = '$ld'
   else:
-    cc = 'gcc'
-    cxx = 'g++'
+    cc = 'cc'
+    cxx = 'c++'
     ld = '$cc'
     ldxx = '$cxx'
     ld_host = '$cc_host'
     ldxx_host = '$cxx_host'
 
   cc_host = None
   cxx_host = None
   cc_host_global_setting = None
   cxx_host_global_setting = None
 
@@ skipping 447 matching lines @@
           arglists.append(
               (target_list, target_dicts, data, params, config_name))
         pool.map(CallGenerateOutputForConfig, arglists)
       except KeyboardInterrupt, e:
         pool.terminate()
         raise e
     else:
       for config_name in config_names:
         GenerateOutputForConfig(target_list, target_dicts, data, params,
                                 config_name)