We only compile and tag cipd packages with armv6, so armv7 hosts get
404s from cipd. This will use armv6 packages on armv7 bots, which should
work.

Bug: 776703
Change-Id: I6e54c2f9e1b220ce038a99af1df28cb6c0a9e579
Reviewed-on: https://chromium-review.googlesource.com/730850Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Benjamin Pastene <bpastene@chromium.org>