Relevant commits:
  d4dc0c29a mac_toolchain: add support for legacy Xcode 8.*

BUG=797051
TBR=vadimsh@chromium.org

Change-Id: I79a77a03b332d7f4bfbe8208928d67194dfc1854
Reviewed-on: https://chromium-review.googlesource.com/897685Reviewed-by: Sergey Berezin <sergeyberezin@chromium.org>
Commit-Queue: Sergey Berezin <sergeyberezin@chromium.org>