- When allocating virtual memory, make sure addresses don't interfere
  with hard-coded sanitizer regions.

Bug: v8:7146
Change-Id: I5bcb664b32bf53c8581772fe329190da6033701f
Reviewed-on: https://chromium-review.googlesource.com/833171Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50208}