Speculative fix for build on windows build bots.

The root of problem is a _cache_temp file.
git_cache expected that it is a folder.
So rmtree failed to remove it.

BUG=
TBR= dpranke@chromium.org, enne@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/825133002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@293502 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/gclient_utils.py b/gclient_utils.py
index 069d5d7..8d4cf3f 100644
--- a/gclient_utils.py
+++ b/gclient_utils.py
@@ -166,6 +166,13 @@
       time.sleep(0.1)
 
 
+def rm_file_or_tree(path):
+  if os.path.isfile(path):
+    os.remove(path)
+  else:
+    rmtree(path)
+
+
 def rmtree(path):
   """shutil.rmtree() on steroids.