Android: Prefix target toolchain names with "android_".

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.
 
 # =============================================================================
 # WHAT IS THIS FILE?
 # =============================================================================
 #
 # This is the master GN build configuration. This file is loaded after the
 # build args (args.gn) for the build directory and after the toplevel ".gn"
@@ skipping 198 matching lines @@
     assert(false, "Unsupported host_os: $host_os")
   }
 }
 
 _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_$target_cpu"
+    _default_toolchain = "//build/toolchain/android:android_clang_$target_cpu"
   } else {
-    _default_toolchain = "//build/toolchain/android:$target_cpu"
+    _default_toolchain = "//build/toolchain/android:android_$target_cpu"
   }
 } else if (target_os == "chromeos" || target_os == "linux") {
   # See comments in build/toolchain/cros/BUILD.gn about board compiles.
   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"
@@ skipping 410 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
   }
 }