Remove build/download_libclang.py

All uses should have been replaced by calls to
update.py --package=libclang by now.

Bug: 884608
Change-Id: I668a32343c50d26eea76555e374e004f95022141
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1917518
Auto-Submit: Hans Wennborg <hans@chromium.org>
Commit-Queue: Reid Kleckner <rnk@chromium.org>
Reviewed-by: Reid Kleckner <rnk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715754}

build/download_libclang.py

-#!/usr/bin/env python
-# Copyright 2017 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 download libclang binaries from google storage."""
-
-import os
-import sys
-
-sys.path.append(os.path.join(os.path.abspath(os.path.dirname(__file__)), '..',
-                             'tools', 'clang', 'scripts'))
-
-import update
-
-# TODO(hans): Remove this forwarding hack after all callers of this script have
-# been updated to call update.py instead.
-if __name__ == '__main__':
-  sys.argv = [sys.argv[0], '--package=libclang']
-  sys.exit(update.main())