Windows was missed in https://golang.org/cl/141600043.

Fixes #6163 (again).

Change-Id: I09076be80fb6b2148d3e5618461ebaa79f27d5b3
Reviewed-on: https://go-review.googlesource.com/39490Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>