Work on GN iOS build.

build/config/BUILDCONFIG.gn

 # Copyright (c) 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.
 
 # =============================================================================
 # BUILD FLAGS
 # =============================================================================
 #
 # This block lists input arguments to the build, along with their default
 # values. GN requires listing them explicitly so it can validate input and have
@@ skipping 62 matching lines @@
   is_lsan = false
 
   # Compile for Memory Sanitizer to find uninitialized reads.
   is_msan = false
 
   # Compile for Thread Sanitizer to find threading bugs.
   is_tsan = false
 
   # When running in gyp-generating mode, this is the root of the build tree.
   gyp_output_dir = "out"
+
+  # When running in gyp-generating mode, this flag indicates if the current GYP
+  # generator is xcode.On Mac, you can assume if this is false that the

[Nico, 2014/01/29 18:34:19]

Nit: missing space after '.', and I'd probably just say "Can only be true on
iOS" as 2nd sentence

+  # generator is Ninja.
+  is_gyp_xcode_generator = false
 }
 
 # =============================================================================
 # OS DEFINITIONS
 # =============================================================================
 #
 # We set these various is_FOO booleans for convenience in writing OS-based
 # conditions.
 #
 # - is_android, is_chromeos, is_ios, and is_win should be obvious.
@@ skipping 61 matching lines @@
   is_win = false
 } else if (os == "ios") {
   is_android = false
   is_chromeos = false
   is_ios = true
   is_linux = false
   is_mac = false
   is_nacl = false
   is_posix = true
   is_win = false
-  if (!is_clang) {
+  if (!is_gyp_xcode_generator) {
     # Always use clang on iOS when using ninja
-    # (which is always true when using GN).
     is_clang = true
   }
 } else if (os == "linux") {
   is_android = false
   is_chromeos = false
   is_ios = false
   is_linux = true
   is_mac = false
   is_nacl = false
   is_posix = true
@@ skipping 148 matching lines @@
 native_compiler_configs = [
   "//build/config:my_msvs",  # TODO(brettw) eraseme
 
   "//build/config/compiler:compiler",
   "//build/config/compiler:chromium_code",
   "//build/config/compiler:default_warnings",
   "//build/config/compiler:no_rtti",
   "//build/config/compiler:runtime_library",
 ]
 if (is_win) {
-  native_compiler_configs += [
-    "//build/config/win:sdk",
-  ]
-} else if (is_clang) {
+  native_compiler_configs += [ "//build/config/win:sdk", ]
+} else if (is_mac) {
+  native_compiler_configs += [ "//build/config/mac:sdk", ]
+} else if (is_ios) {
+  native_compiler_configs += [ "//build/config/ios:sdk", ]
+}
+if (is_clang) {
   native_compiler_configs += [ "//build/config/clang:find_bad_constructs" ]
 }
 
 # Optimizations and debug checking.
 if (is_debug) {
   native_compiler_configs += [ "//build/config:debug" ]
   default_optimization_config = "//build/config/compiler:no_optimize"
 } else {
   native_compiler_configs += [ "//build/config:release" ]
   default_optimization_config = "//build/config/compiler:optimize"
@@ skipping 91 matching lines @@
 } else if (is_android) {
   host_toolchain = "//build/toolchain/linux:$build_cpu_arch"
   set_default_toolchain("//build/toolchain/android:$cpu_arch")
 } else if (is_linux) {
   host_toolchain = "//build/toolchain/linux:$build_cpu_arch"
   set_default_toolchain("//build/toolchain/linux:$cpu_arch")
 } else if (is_mac || is_ios) {
   host_toolchain = "//build/toolchain/mac:clang"
   set_default_toolchain(host_toolchain)
 }