We no longer support linux-386 and there are no CIPD builders that build
packages for it.

R=tandrii@chromium.org
BUG=854300

Change-Id: Ibfefee828118c898432784c8ef3dd5894a28cfaa
Reviewed-on: https://chromium-review.googlesource.com/1110845Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>