Add support for git_cl_tests on Windows platform

Change-Id: I9d3d084e7f48ab991db3db16873f030890ad72d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2108981
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
diff --git a/gerrit_util.py b/gerrit_util.py
index 2c79018..d22c7f1 100644
--- a/gerrit_util.py
+++ b/gerrit_util.py
@@ -206,7 +206,7 @@
       return subprocess2.check_output(
           ['git', 'config', '--path', 'http.cookiefile']).strip()
     except subprocess2.CalledProcessError:
-      return os.path.join(os.environ['HOME'], '.gitcookies')
+      return os.path.expanduser(os.path.join('~', '.gitcookies'))
 
   @classmethod
   def _get_gitcookies(cls):