v8: pull fix for builtin code size on PPC

Pull in the change that has been committed to v8 master in
https://codereview.chromium.org/1415463002/.  We are currently
cherry-picking into 4.6 and 4.7 but until next next v8 update
into Node Master I'd like to float it as it will make PPC LE
go green in the CI

Fixes: https://github.com/nodejs/node/issues/3390


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <ben@strongloop.com>
PR-URL: https://github.com/nodejs/node/pull/3474