GitLab

Let users specify the logging location. The switch name is intentionally
left generic to allow other binaries to use the same flag.

Bug: 760431
Change-Id: I5f03f146b090fa5ba0e21718aeb27f5780981dde
Reviewed-on: https://chromium-review.googlesource.com/647314Reviewed-by: Nick Carter <nick@chromium.org>
Commit-Queue: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503645}