Bug fixed:

- Remove builtins/builtins-<arch>.cc from v8_base.
- Add missing builtins/builtins-x87.cc to v8_builtins_generators.

Bug: v8:6055
Change-Id: I55da82f740df9294d83ec188770ee7a6e0e60941
Reviewed-on: https://chromium-review.googlesource.com/509429Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Loo Rong Jie <loorongjie@gmail.com>
Cr-Commit-Position: refs/heads/master@{#45456}