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

build/android/create_standalone_apk_action.gypi

+# 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.
+
+# This file is meant to be included into an action to provide an action that
+# combines a directory of shared libraries and an incomplete APK into a
+# standalone APK.
+#
+# To use this, create a gyp action with the following form:
+#  {
+#    'action_name': 'some descriptive action name',
+#    'variables': {
+#      'inputs': [ 'input_path1', 'input_path2' ],
+#      'input_apk_path': '<(unsigned_apk_path)',
+#      'output_apk_path': '<(unsigned_standalone_apk_path)',
+#      'libraries_top_dir': '<(libraries_top_dir)',
+#    },
+#    'includes': [ 'relative/path/to/create_standalone_apk_action.gypi' ],
+#  },
+
+{
+  'message': 'Creating standalone APK: <(output_apk_path)',
+  'variables': {
+    'inputs': [],
+  },
+  'inputs': [
+    '<(DEPTH)/build/android/gyp/util/build_utils.py',
+    '<(DEPTH)/build/android/gyp/create_standalone_apk.py',
+    '<(input_apk_path)',
+    '>@(inputs)',
+  ],
+  'outputs': [
+    '<(output_apk_path)',
+  ],
+  'action': [
+    'python', '<(DEPTH)/build/android/gyp/create_standalone_apk.py',
+    '--libraries-top-dir=<(libraries_top_dir)',
+    '--input-apk-path=<(input_apk_path)',
+    '--output-apk-path=<(output_apk_path)',
+  ],
+}