v8 now uses the same SDK as Chromium, even when built as a standalone project.
The deployment target override has no effect.

Bug: chromium:740693
Change-Id: I089f74d5ad1590ff7167564f83b0110620a92ef9
Reviewed-on: https://chromium-review.googlesource.com/565887Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46686}