Add a snapshot of flutter/engine/src/build to our sdk

build/install-android-sdks.sh

+#!/bin/bash -e
+
+# Copyright (c) 2012 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.
+
+# Script to install SDKs needed to build chromium on android.
+# See http://code.google.com/p/chromium/wiki/AndroidBuildInstructions
+
+echo 'checking for sdk packages install'
+# Use absolute path to call 'android' so script can be run from any directory.
+cwd=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
+# Get the SDK extras packages to install from the DEPS file 'sdkextras' hook.
+packages="$(python ${cwd}/get_sdk_extras_packages.py)"
+if [[ -n "${packages}" ]]; then
+  ${cwd}/../third_party/android_tools/sdk/tools/android update sdk --no-ui \
+      --filter ${packages}
+fi
+
+echo "install-android-sdks.sh complete."