v8: pull fix for builtin code size on PPC
Fixes: https://github.com/nodejs/node/issues/3390
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