[infra] Fixes for cross-toolchains

DEPS

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 vars = {
   # The dart_root is the root of our sdk checkout. This is normally
   # simply sdk, but if using special gclient specs it can be different.
   "dart_root": "sdk",
 
   # We use mirrors of all github repos to guarantee reproducibility and
@@ skipping 28 matching lines @@
   # Revisions of /third_party/* dependencies.
   "angular_analyzer_plugin_tag": "@v0.0.7",
   "args_tag": "@0.13.7",
   "async_tag": "@1.13.0",
   "barback-0.13.0_rev": "@34853",
   "barback-0.14.0_rev": "@36398",
   "barback-0.14.1_rev": "@38525",
   "barback_tag" : "@0.15.2+9",
   "bazel_worker_tag": "@0.1.2",
   "boolean_selector_tag" : "@1.0.2",
-  "boringssl_gen_rev": "@1a810313a0290e1caace9da73fa3ab89995ad2c7",
+  "boringssl_gen_rev": "@753224969dbe43dad29343146529727b5066c0f3",
   "boringssl_rev" : "@d519bf6be0b447fb80fbc539d4bff4479b5482a2",
   "charcode_tag": "@v1.1.1",
   "chrome_rev" : "@19997",
   "cli_util_tag" : "@0.0.1+3",
   "code_transformers_tag": "@v0.5.1",
   "collection_tag": "@1.13.0",
   "convert_tag": "@2.0.1",
   "crypto_tag" : "@2.0.1",
   "csslib_tag" : "@0.13.3+1",
   "dart2js_info_tag" : "@0.5.3+1",
@@ skipping 538 matching lines @@
     # Update the Windows toolchain if necessary.
     'name': 'win_toolchain',
     'pattern': '.',
     'action': ['python', 'sdk/build/vs_toolchain.py', 'update'],
   },
   {
     "pattern": ".",
     "action": ["python", Var("dart_root") + "/tools/generate_buildfiles.py"],
   },
 ]