Fix build output directories in GN.

build/toolchain/android/BUILD.gn

 # Copyright 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.
 
 import("../clang.gni")
 import("../goma.gni")
 import("../gcc_toolchain.gni")
 
 # Get the location of the Android tools in our tree.
 android_ndk_root =
   rebase_path("//third_party/android_tools/ndk", ".", "")
-android_sdk_root =
-  rebase_path("//third_party/android_tools/sdk", ".", "")
 
 # Get the Android version of the name of the build host's architecture.
 if (build_cpu_arch == "x64") {
   android_host_arch = "x86_64"
 } else if (build_cpu_arch == "x86") {
   android_host_arch = "x86"
 } else {
   assert(false, "Need Android toolchain support for your build OS.")
 }
 
 if (is_gyp) {
   # Set the compilers for GYP to use. This logic is only relevant to GYP where
   # there is "a" target compiler. In native GN builds, we have separate
   # compilers for the toolchains below, any or all of which could be active in
   # any given build.
   if (is_clang) {
     # Set the GYP header for all toolchains when running under Clang.
     gyp_header = make_clang_global_settings
   } else {
     # Find the compiler for GYP for non-Clang Android.
     if (cpu_arch == "x86") {
       android_toolchain_arch = "x86-4.6"
     } else if (cpu_arch == "arm") {
       android_toolchain_arch = "arm-linux-androideabi-4.6"
     } else {
       assert(false, "Need Android toolchain support for your platform.")
     }
 
+    # The extra slash before "toolchains" is because GYP generates this and we
+    # have to match the make_global_settings character-for-character,
+    # TODO(brettw) remove extra slash before toolchains when GYP compat is no
+    # longer necessary.
     android_toolchain =
-      "$android_ndk_root/toolchains/$android_toolchain_arch/prebuilt/$build_os-$android_host_arch/bin"
+      "$android_ndk_root//toolchains/$android_toolchain_arch/prebuilt/$build_os-$android_host_arch/bin"
 
     # This script will find the compilers for the given Android toolchain
     # directory.
     android_compilers = exec_script("find_android_compiler.py",
                                     [android_toolchain], "value")
     gyp_header =
       "'make_global_settings': [" +
       "['CC', '" + android_compilers[0] + "']," +
       "['CXX', '" + android_compilers[1] + "']," +
       "['CC.host', '" + android_compilers[2] + "']," +
@@ skipping 36 matching lines @@
 gcc_toolchain("arm") {
   prefix = "$android_ndk_root/toolchains/arm-linux-androideabi-4.6/prebuilt/$build_os-$android_host_arch/bin/arm-linux-androideabi-"
   cc  = prefix + "gcc"
   cxx = prefix + "g++"
   ar  = prefix + "ar"
   ld  = cxx
 
   toolchain_cpu_arch = "arm"
   toolchain_os = "android"
 }