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

build/build-ctags.sh

+#!/bin/bash
+
+# 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.
+
+if [[ a"`ctags --version | head -1 | grep \"^Exuberant Ctags\"`" == "a" ]]; then
+  cat <<EOF
+  You must be using Exuberant Ctags, not just standard GNU ctags. If you are on
+  Debian or a related flavor of Linux, you may want to try running
+  apt-get install exuberant-ctags.
+EOF
+  exit
+fi
+
+CHROME_SRC_DIR="$PWD"
+
+fail() {
+  echo "Failed to create ctags for $1"
+  exit 1
+}
+
+ctags_cmd() {
+  echo "ctags --languages=C++ $1 --exclude=.git -R -f .tmp_tags"
+}
+
+build_dir() {
+  local extraexcludes=""
+  if [[ a"$1" == "a--extra-excludes" ]]; then
+    extraexcludes="--exclude=third_party --exclude=build --exclude=out"
+    shift
+  fi
+
+  cd "$CHROME_SRC_DIR/$1" || fail $1
+  # Redirect error messages so they aren't seen because they are almost always
+  # errors about components that you just happen to have not built (NaCl, for
+  # example).
+  $(ctags_cmd "$extraexcludes") 2> /dev/null || fail $1
+  mv -f .tmp_tags tags
+}
+
+# We always build the top level but leave all submodules as optional.
+build_dir --extra-excludes "" "top level"
+
+# Build any other directies that are listed on the command line.
+for dir in $@; do
+  build_dir "$1"
+  shift
+done