android: Make 64-bit chromes compile with clang.

build/config/android/config.gni

 # Copyright 2014 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.
 
 # This file contains common system config stuff for the Android build.
 
 if (is_android) {
   assert(rebase_path("//", root_build_dir) == "../../",
          "Android output directory must be nested 2 levels within src/ (" +
              "e.g.: out-gn/Debug). http://crbug.com/412935")
@@ skipping 178 matching lines @@
   android_sdk_build_tools =
       "${android_sdk_root}/build-tools/$android_sdk_build_tools_version"
 
   # Path to the SDK's android.jar
   android_sdk_jar = "$android_sdk/android.jar"
 
   zipalign_path = "$android_sdk_build_tools/zipalign"
 
   # Subdirectories inside android_ndk_root that contain the sysroot for the
   # associated platform.
+  # If you raise this, reevaluate the snprintf=snprintf in ./BUILD.gn.
   _android_api_level = 16
   x86_android_sysroot_subdir =
       "platforms/android-${_android_api_level}/arch-x86"
   arm_android_sysroot_subdir =
       "platforms/android-${_android_api_level}/arch-arm"
   mips_android_sysroot_subdir =
       "platforms/android-${_android_api_level}/arch-mips"
+
+  # If you raise this, reevaluate the snprintf=snprintf in ./BUILD.gn.
   _android64_api_level = 21
   x86_64_android_sysroot_subdir =
       "platforms/android-${_android64_api_level}/arch-x86_64"
   arm64_android_sysroot_subdir =
       "platforms/android-${_android64_api_level}/arch-arm64"
   mips64_android_sysroot_subdir =
       "platforms/android-${_android64_api_level}/arch-mips64"
 
   # Toolchain root directory for each build. The actual binaries are inside
   # a "bin" directory inside of these.
@@ skipping 112 matching lines @@
           "//build/toolchain/android:${android_secondary_abi_cpu}"
     }
   }
 }
 
 declare_args() {
   # Enables used resource whitelist generation. Set for official builds only
   # as a large amount of build output is generated.
   enable_resource_whitelist_generation = is_android && is_official_build
 }