... to please mksnapshot which expects the new space to be empty.

Bug: v8:10470
Change-Id: I7d5b62db138ef2e334581a8697d137cd13291d7c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3827877
Auto-Submit: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82440}