Remove toolchain definition to build with gcc on Mac.

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 (!use_xcode_clang) {
+  compiler_prefix = compiler_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
   }
 }
@@ skipping 25 matching lines @@
                             root_build_dir),
                 "trim scope")
 
 # Work around for unused variable warning in template https://crbug.com/395883.
 assert(tool_versions != "")
 
 # Shared toolchain definition. Invocations should set toolchain_os to set the
 # build args in this definition.
 template("mac_toolchain") {
   toolchain(target_name) {
-    assert(defined(invoker.cc), "mac_toolchain() must specify a \"cc\" value")
-    assert(defined(invoker.cxx), "mac_toolchain() must specify a \"cxx\" value")
-    assert(defined(invoker.ld), "mac_toolchain() must specify a \"ld\" value")
     assert(defined(invoker.toolchain_cpu),
            "mac_toolchain() must specify a \"toolchain_cpu\"")
     assert(defined(invoker.toolchain_os),
            "mac_toolchain() must specify a \"toolchain_os\"")
 
     # concurrent_links is picked up from the declare_arg().
 
-    # We can't do string interpolation ($ in strings) on things with dots in
-    # them. To allow us to use $cc below, for example, we create copies of
-    # these values in our scope.
-    cc = invoker.cc
-    cxx = invoker.cxx
-    ld = invoker.ld
+    cc = "${compiler_prefix}clang"
+    cxx = "${compiler_prefix}clang++"
+    ld = cxx
 
     linker_driver =
         "TOOL_VERSION=${tool_versions.linker_driver} " +
         rebase_path("//build/toolchain/mac/linker_driver.py", root_build_dir)
 
     # Make these apply to all tools below.
     lib_switch = "-l"
     lib_dir_switch = "-L"
 
     # Object files go in this directory. Use label_name instead of
@@ skipping 237 matching lines @@
     }
 
     toolchain_args() {
       current_cpu = invoker.toolchain_cpu
       current_os = invoker.toolchain_os
 
       # These values need to be passed through unchanged.
       host_toolchain = host_toolchain
       target_os = target_os
       target_cpu = target_cpu
-
-      if (defined(invoker.is_clang)) {
-        is_clang = invoker.is_clang
-      }
+      is_clang = true
     }
   }
 }
 
 mac_toolchain("clang_arm") {
   toolchain_cpu = "arm"
   toolchain_os = "mac"
-  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"
-  cc = "${compiler_prefix}${_clang_prefix}clang"
-  cxx = "${compiler_prefix}${_clang_prefix}clang++"
-  ld = cxx
-  is_clang = true
+  toolchain_os = "ios"
 }
 
 mac_toolchain("ios_clang_arm64") {
   toolchain_cpu = "arm64"
-  toolchain_os = "mac"
-  cc = "${compiler_prefix}${_clang_prefix}clang"
-  cxx = "${compiler_prefix}${_clang_prefix}clang++"
-  ld = cxx
-  is_clang = true
+  toolchain_os = "ios"
 }
 
 mac_toolchain("ios_clang_x86") {
   toolchain_cpu = "x86"
-  toolchain_os = "mac"
-  cc = "${compiler_prefix}${_clang_prefix}clang"
-  cxx = "${compiler_prefix}${_clang_prefix}clang++"
-  ld = cxx
-  is_clang = true
+  toolchain_os = "ios"
 }
 
 mac_toolchain("ios_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
+  toolchain_os = "ios"
 }