GitLab

Simplify the logic in the mini_installer BUILD.gn file

A lot of the logic in this file dates from the Syzygy days, as we don't
use it anymore there's no need to template the target that generates the
installer.

Change-Id: I810e059b6eb733324096389dca53853f080c672d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2613328
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841558}