gcc builds seem to have troubles with this:

 error: call to non-constexpr function

Remove the UNREACHABLE() calls for now but keep a TODO to
potentially re-enable them again once we've figured this out.

Bug: v8:7700,v8:12667
Change-Id: I9628a1326c1c4200b90aad25cd2eabfeb06608fb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3494237
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79314}