Throw away everything in the go workspace except bin (2nd attempt).

Trying a more reliable way of deleting directories on Windows.
The attempt in doesn't
seem to help on the bots.


Review URL: .
diff --git a/ b/
index 2758b1f..95ae532 100755
--- a/
+++ b/
@@ -45,7 +45,8 @@
   go_bin_dir = os.path.join(golang_workspace, 'bin')
   tmp_dir = tempfile.mkdtemp()
   shutil.move(go_bin_dir, tmp_dir)
-  shutil.rmtree(golang_workspace)
+  utils.RemoveDirectory(golang_workspace)
+  os.makedirs(golang_workspace)
   shutil.move(os.path.join(tmp_dir, 'bin'), go_bin_dir)