ninja expects the output of an action to update the timestamp, however
a plain copy does not do this. So on a second run, ninja sees the
timestamp of the copy .bat is newer than the dll (original publish date)
so it re-copies. To avoid this, `touch` the dll on copy.

BUG=453037
Change-Id: Icb849d2b0faaceeccfc33e2eda509c835c9cdc93
Reviewed-on: https://chromium-review.googlesource.com/244040Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Scott Graham <scottmg@chromium.org>