Clean up default toolchain logic for CrOS GN builds.

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.
 
 # =============================================================================
 # PLATFORM SELECTION
 # =============================================================================
 #
 # There are two main things to set: "os" and "cpu". The "toolchain" is the name
 # of the GN thing that encodes combinations of these things.
@@ skipping 185 matching lines @@
 _default_toolchain = ""
 
 if (target_os == "android") {
   assert(host_os == "linux" || host_os == "mac",
          "Android builds are only supported on Linux and Mac hosts.")
   if (is_clang) {
     _default_toolchain = "//build/toolchain/android:clang_$target_cpu"
   } else {
     _default_toolchain = "//build/toolchain/android:$target_cpu"
   }
-} else if (target_os == "chromeos") {
+} else if (target_os == "chromeos" || target_os == "linux") {
   # See comments in build/toolchain/cros/BUILD.gn about board compiles.
-  assert(host_os == "linux",
-         "ChromeOS builds are only supported on Linux hosts.")
-  if (is_clang) {
-    _default_toolchain = "//build/toolchain/cros:clang_target"
-  } else {
-    _default_toolchain = "//build/toolchain/cros:target"
-  }
-} else if (target_os == "ios") {
-  _default_toolchain = "//build/toolchain/mac:ios_clang_$target_cpu"
-} else if (target_os == "linux") {
   if (is_clang) {
     _default_toolchain = "//build/toolchain/linux:clang_$target_cpu"
   } else {
     _default_toolchain = "//build/toolchain/linux:$target_cpu"
   }
+} else if (target_os == "ios") {
+  _default_toolchain = "//build/toolchain/mac:ios_clang_$target_cpu"
 } else if (target_os == "mac") {
   assert(host_os == "mac", "Mac cross-compiles are unsupported.")
   _default_toolchain = host_toolchain
 } else if (target_os == "win") {
   # On Windows we use the same toolchain for host and target by default.
   assert(target_os == host_os, "Win cross-compiles only work on win hosts.")
   if (is_clang) {
     _default_toolchain = "//build/toolchain/win:clang_$target_cpu"
   } else {
     _default_toolchain = "//build/toolchain/win:$target_cpu"
@@ skipping 397 matching lines @@
 set_defaults("component") {
   if (is_component_build) {
     configs = default_shared_library_configs
     if (is_android) {
       configs -= [ "//build/config/android:hide_native_jni_exports" ]
     }
   } else {
     configs = default_compiler_configs
   }
 }