Temp dir used to download gsutil seems somehow hit max path length limit
on Windows builders.

Bug: 1264242
Change-Id: Ib924932542dbbe68f4ef58ca604724dcb645330f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3247566
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Junji Watanabe <jwata@google.com>
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Owners-Override: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Junji Watanabe <jwata@google.com>
Reviewed-by: Fumitoshi Ukai <ukai@google.com>