This'll make the workflow more flexible as in GN world, the builddir
is often not in the currently hardcoded out/Release.

NOTRY=true

Bug: chromium:645890
Change-Id: Id2afc8d8fea322ac98b65b7e9d28a2ba8c0dd0ac
Reviewed-on: https://chromium-review.googlesource.com/549899
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46258}