Use gclient's git_cache setting in bot_update/api.py

recipe_modules/gclient/config.py

 # 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.
 
 import types
 
 from recipe_engine.config import config_item_context, ConfigGroup, BadConf
 from recipe_engine.config import ConfigList, Dict, Single, Static, Set, List
 
 from . import api as gclient_api
@@ skipping 151 matching lines @@
 @config_ctx(includes=['chromium_bare'])
 def chromium_empty(c):
   c.solutions[0].deps_file = ''  # pragma: no cover
 
 @config_ctx(includes=['chromium_bare'])
 def chromium(c):
   s = c.solutions[0]
   s.custom_deps = mirror_only(c, {})
 
 @config_ctx(includes=['chromium'])
+def chromium_no_git_cache(c):
+  c.cache_dir = None
+
+@config_ctx(includes=['chromium'])
 def chromium_lkcr(c):
   # TODO(phajdan.jr): Add git hashes for LKCR crbug.com/349277.
   if c.GIT_MODE:
     raise BadConf('Git has problems with safesync_url and LKCR, '
                   'crbug.com/349277 crbug.com/109191')  # pragma: no cover
   s = c.solutions[0]
   s.safesync_url = 'https://build.chromium.org/p/chromium/lkcr-status/lkgr'
   # TODO(hinoka): Once lkcr exists and is a tag, it should just be lkcr
   #               rather than origin/lkcr.
   s.revision = 'origin/lkcr'
@@ skipping 460 matching lines @@
   soln = c.solutions.add()
   soln.name = 'gerrit-test-cq-normal'
   soln.url = 'https://chromium.googlesource.com/playground/gerrit-cq/normal.git'
 
 # TODO(phajdan.jr): Move to proper repo and add coverage.
 @config_ctx()
 def valgrind(c):  # pragma: no cover
   """Add Valgrind binaries to the gclient solution."""
   c.solutions[0].custom_deps['src/third_party/valgrind'] = \
     ChromiumGitURL(c, 'chromium', 'deps', 'valgrind', 'binaries')