Never use the hermetic xcode toolchain for iOS recipes.

scripts/slave/recipe_modules/chromium/config.py

 # Copyright 2013 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 pipes
 
 from recipe_engine.config import config_item_context, ConfigGroup
 from recipe_engine.config import Dict, List, Single, Static, Set, BadConf
 from recipe_engine.config_types import Path
 
@@ skipping 45 matching lines @@
       GYP_CROSSCOMPILE = Single(int, jsonish_fn=str, required=False),
       GYP_CHROMIUM_NO_ACTION = Single(int, jsonish_fn=str, required=False),
       GYP_DEFINES = Dict(equal_fn, ' '.join, (basestring,int,Path)),
       GYP_GENERATORS = Set(basestring, ','.join),
       GYP_GENERATOR_FLAGS = Dict(equal_fn, ' '.join, (basestring,int)),
       GYP_INCLUDE_LAST = Single(Path, required=False),
       GYP_LINK_CONCURRENCY = Single(int, required=False),
       GYP_MSVS_VERSION = Single(basestring, required=False),
       GYP_USE_SEPARATE_MSPDBSRV = Single(int, jsonish_fn=str, required=False),
       LLVM_DOWNLOAD_GOLD_PLUGIN = Single(int, required=False),
-      FORCE_MAC_TOOLCHAIN = Single(int, required=False),
     ),
     env = ConfigGroup(
       PATH = List(Path),
       ADB_VENDOR_KEYS = Single(Path, required=False),
       LLVM_FORCE_HEAD_REVISION = Single(basestring, required=False),
       GOMA_STUBBY_PROXY_IP_ADDRESS = Single(basestring, required=False),
       FORCE_MAC_TOOLCHAIN = Single(int, required=False),
     ),
     project_generator = ConfigGroup(
       tool = Single(basestring, empty_val='gyp'),
@@ skipping 152 matching lines @@
 def ninja(c):
   if c.TARGET_PLATFORM == 'ios':
     c.gyp_env.GYP_GENERATORS.add('ninja')
 
   out_path = 'out'
   if c.TARGET_CROS_BOARD:
     out_path += '_%s' % (c.TARGET_CROS_BOARD,)
   c.build_dir = c.CHECKOUT_PATH.join(out_path)
 
 @config_ctx()
+def force_mac_toolchain_off(c):
+  c.env.FORCE_MAC_TOOLCHAIN = 0
+
+@config_ctx()
 def msvs2013(c):
   c.gn_args.append('visual_studio_version=2013')
   c.gyp_env.GYP_MSVS_VERSION = '2013'
 
 @config_ctx()
 def msvs2015(c):
   c.gn_args.append('visual_studio_version=2015')
   c.gyp_env.GYP_MSVS_VERSION = '2015'
 
 @config_ctx()
@@ skipping 555 matching lines @@
 def cast_linux(c):
   c.gyp_env.GYP_DEFINES['chromecast'] = 1
 
 @config_ctx()
 def internal_gles2_conform_tests(c):
   c.gyp_env.GYP_DEFINES['internal_gles2_conform_tests'] = 1
 
 @config_ctx()
 def build_angle_deqp_tests(c):
   c.gyp_env.GYP_DEFINES['build_angle_deqp_tests'] = 1