... to let C++ compiler know that isolate root is 4Gb aligned and give
it a chance to generate a better code.

Bug: v8:9353
Change-Id: Ibd23c14cc44107c722a446a84dd14ca66f3bccfe
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1776079Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63445}