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/git_cache.py b/git_cache.py
index b2de8ba..cb7f7e3 100755
--- a/git_cache.py
+++ b/git_cache.py
@@ -312,7 +312,7 @@
           retcode = 0
     finally:
       # Clean up the downloaded zipfile.
-      gclient_utils.rmtree(tempdir)
+      gclient_utils.rm_file_or_tree(tempdir)
 
     if retcode:
       self.print(
@@ -486,7 +486,7 @@
                      if os.path.isdir(os.path.join(cachepath, path))])
     for dirent in dirlist:
       if dirent.startswith('_cache_tmp') or dirent.startswith('tmp'):
-        gclient_utils.rmtree(os.path.join(cachepath, dirent))
+        gclient_utils.rm_file_or_tree(os.path.join(cachepath, dirent))
       elif (dirent.endswith('.lock') and
           os.path.isfile(os.path.join(cachepath, dirent))):
         repo_dirs.add(os.path.join(cachepath, dirent[:-5]))