Pure refactoring. The re-organization allows to easily
add more platforms.

Bug: chromium:1056170
Change-Id: Ia191c37a1dabff6952414c5314beeeae881713b7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2129636Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66924}