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

Trying a more reliable way of deleting directories on Windows.
The attempt in https://codereview.chromium.org/1680173002/ doesn't
seem to help on the bots.

BUG=585462
TBR=phoglund@chromium.org

Review URL: https://codereview.chromium.org/1686753002 .

build_apprtc_collider.py

diff --git a/build_apprtc_collider.py b/build_apprtc_collider.py
index 2758b1f..95ae532 100755
--- a/build_apprtc_collider.py
+++ b/build_apprtc_collider.py
@@ -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)
   os.rmdir(tmp_dir)