Until now, when generating a builtin, it can only embed builtins
(as call targets) that have already been generated. This is either
achieved by reordering the builtins list, or by loading the call
target at runtime from the builtins list (see
MacroAssembler::TailCallBuiltin).

This patch works around this issue by filling the builtins list
with dummy code objects, which are later replaced with the completed
actual builtins. In release mode, this adds around 3ms to 140ms we
previously needed to populate the builtins list. 

Change-Id: I7d451b3c09a1db4b9e755548102a80c7f0dfada2
Reviewed-on: https://chromium-review.googlesource.com/586531
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47062}