[iOS/GN] Allow compilation with system clang.

build/toolchain/mac/BUILD.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.
 
 # TODO(brettw) Use "gcc_toolchain.gni" like the Linux toolchains. This requires
 # some enhancements since the commands on Mac are slightly different than on
 # Linux.
 
 import("../goma.gni")
 import("//build/config/ios/ios_sdk.gni")
 import("//build/config/mac/mac_sdk.gni")
 import("//build/config/mac/symbols.gni")
 
 assert(host_os == "mac")
 
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 import("//build/toolchain/concurrent_links.gni")
 
 if (use_goma) {
   assert(cc_wrapper == "", "Goma and cc_wrapper can't be used together.")
   compiler_prefix = "$goma_dir/gomacc "
 } else if (cc_wrapper != "") {
   compiler_prefix = cc_wrapper + " "
 } else {
   compiler_prefix = ""
 }
 
+if (use_xcode_clang) {
+  _clang_prefix = ""
+} else {
+  _clang_prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin/",
+                              root_build_dir)
+}
+
 if (current_toolchain == default_toolchain) {
   # Reduce the number of tasks using the copy_bundle_data and compile_xcassets
   # tools as they can cause lots of I/O contention when invoking ninja with a
   # large number of parallel jobs (e.g. when using distributed build like goma).
   pool("bundle_pool") {
     depth = concurrent_links
   }
 }
 
 # This will copy the gyp-mac-tool to the build directory. We pass in the source
@@ skipping 307 matching lines @@
       if (defined(invoker.is_clang)) {
         is_clang = invoker.is_clang
       }
     }
   }
 }
 
 mac_toolchain("clang_arm") {
   toolchain_cpu = "arm"
   toolchain_os = "mac"
-  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                       root_build_dir)
-  cc = "${compiler_prefix}$prefix/clang"
-  cxx = "${compiler_prefix}$prefix/clang++"
+  cc = "${compiler_prefix}${_clang_prefix}clang"
+  cxx = "${compiler_prefix}${_clang_prefix}clang++"
   ld = cxx
   is_clang = true
 }
 
+mac_toolchain("arm") {
+  toolchain_cpu = "arm"
+  toolchain_os = "mac"
+  cc = "${compiler_prefix}gcc"
+  cxx = "${compiler_prefix}g++"
+  ld = cxx
+  is_clang = false
+}
+
+mac_toolchain("clang_x64") {
+  toolchain_cpu = "x64"
+  toolchain_os = "mac"
+  cc = "${compiler_prefix}${_clang_prefix}clang"
+  cxx = "${compiler_prefix}${_clang_prefix}clang++"
+  ld = cxx
+  is_clang = true
+}
+
+mac_toolchain("x64") {
+  toolchain_cpu = "x64"
+  toolchain_os = "mac"
+  cc = "${compiler_prefix}gcc"
+  cxx = "${compiler_prefix}g++"
+  ld = cxx
+  is_clang = false
+}
+
 mac_toolchain("ios_clang_arm") {
   toolchain_cpu = "arm"
   toolchain_os = "mac"
-
-  # TODO(GYP): We need to support being able to use the version of clang
-  # shipped w/ XCode instead of the one pulled from upstream.
-  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                       root_build_dir)
-  cc = "${compiler_prefix}$prefix/clang"
-  cxx = "${compiler_prefix}$prefix/clang++"
-  ld = cxx
-  is_clang = true
-}
-
-mac_toolchain("ios_clang_armv7") {
-  toolchain_cpu = "armv7"
-  toolchain_os = "mac"
-
-  # TODO(GYP): We need to support being able to use the version of clang
-  # shipped w/ XCode instead of the one pulled from upstream.
-  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                       root_build_dir)
-  cc = "${compiler_prefix}$prefix/clang"
-  cxx = "${compiler_prefix}$prefix/clang++"
+  cc = "${compiler_prefix}${_clang_prefix}clang"
+  cxx = "${compiler_prefix}${_clang_prefix}clang++"
   ld = cxx
   is_clang = true
 }
 
 mac_toolchain("ios_clang_arm64") {
   toolchain_cpu = "arm64"
   toolchain_os = "mac"
-
-  # TODO(GYP): We need to support being able to use the version of clang
-  # shipped w/ XCode instead of the one pulled from upstream.
-  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                       root_build_dir)
-  cc = "${compiler_prefix}$prefix/clang"
-  cxx = "${compiler_prefix}$prefix/clang++"
+  cc = "${compiler_prefix}${_clang_prefix}clang"
+  cxx = "${compiler_prefix}${_clang_prefix}clang++"
   ld = cxx
   is_clang = true
 }
 
-mac_toolchain("arm") {
-  toolchain_cpu = "arm"
+mac_toolchain("ios_clang_x86") {
+  toolchain_cpu = "x86"
   toolchain_os = "mac"
-  cc = "${compiler_prefix}/gcc"
-  cxx = "${compiler_prefix}/g++"
-  ld = cxx
-  is_clang = false
-}
-
-mac_toolchain("clang_x64") {
-  toolchain_cpu = "x64"
-  toolchain_os = "mac"
-  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                       root_build_dir)
-  cc = "${compiler_prefix}$prefix/clang"
-  cxx = "${compiler_prefix}$prefix/clang++"
+  cc = "${compiler_prefix}${_clang_prefix}clang"
+  cxx = "${compiler_prefix}${_clang_prefix}clang++"
   ld = cxx
   is_clang = true
 }
 
-mac_toolchain("x64") {
+mac_toolchain("ios_clang_x64") {
   toolchain_cpu = "x64"
   toolchain_os = "mac"
-  cc = "${compiler_prefix}/gcc"
-  cxx = "${compiler_prefix}/g++"
+  cc = "${compiler_prefix}${_clang_prefix}clang"
+  cxx = "${compiler_prefix}${_clang_prefix}clang++"
   ld = cxx
-  is_clang = false
+  is_clang = true
 }