This ensures that we have a clean slate when updating to newer V8.

TBR=machenbach@chromium.org

Bug: v8:8584
Change-Id: I37f6e4a42738e5e9ea5bfdca5465d6a3e984fe65
Reviewed-on: https://chromium-review.googlesource.com/c/1378169Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58242}