Never use the hermetic xcode toolchain for iOS recipes.

scripts/slave/recipe_modules/ios/api.py

 # Copyright 2015 The Chromium 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 copy
 
 from recipe_engine import recipe_api
 
 
 class iOSApi(recipe_api.RecipeApi):
@@ skipping 213 matching lines @@
     cfg = self.m.chromium.make_config()
 
     if self.using_gyp:
       cfg.gyp_env.GYP_CROSSCOMPILE = 1
       if isinstance(self.__config['GYP_DEFINES'], dict):
         cfg.gyp_env.GYP_DEFINES = copy.deepcopy(self.__config['GYP_DEFINES'])
       else:
         cfg.gyp_env.GYP_DEFINES = dict(v.split('=') for
                                        v in self.__config['GYP_DEFINES'])
     self.m.chromium.c = cfg
+    self.m.chromium.apply_config('force_mac_toolchain_off')
 
     use_goma = (cfg.gyp_env.GYP_DEFINES.get('use_goma') == '1' or
                 'use_goma=true' in self.__config['gn_args'])
     if use_goma:
       # Make sure these chromium configs are applied consistently for the
       # rest of the recipe; they are needed in order for m.chromium.compile()
       # to work correctly.
       self.m.chromium.apply_config('ninja')
       self.m.chromium.apply_config('default_compiler')
       self.m.chromium.apply_config('goma')
@@ skipping 566 matching lines @@
   @property
   def most_recent_iossim(self):
     """Returns the path to the most recently compiled iossim."""
     platform = {
       'device': 'iphoneos',
       'simulator': 'iphonesimulator',
     }[self.platform]
 
     return self.m.path.join(
       'src', 'out', '%s-%s' % (self.configuration, platform), 'iossim')