The hello world sample needs to initialize V8's default platform in case
it is not built as stand-alone example.

Bug: v8:12427
Change-Id: I78b68fbed2c2a25b0ff03675beb94dfc5b9b4135
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3412088Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78756}