By using RWX memory to write we've likely managed to avoid the largest
part of the cost on Intel CPUs.

Bug: v8:11420
Change-Id: Ibf571abc136fc97b3e6429fe42ebf4cfc423b458
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2824443
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73947}