Code generation introduces indirections if a builder exists (and the
serializer is active). These indirections are not necessary outside of
embedded builtins (e.g. in bytecode handlers), so let's reduce its
lifetime.

Bug: v8:6666
Change-Id: I57207012997786f599f79f0982da61eea26f3e22
Reviewed-on: https://chromium-review.googlesource.com/1059114
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53194}