Basically we just need to do the following
# 1. Install v8 ourselves
$ brew install v8-315
# 2. Install libv8 using the v8 binary we just installed
$ gem install libv8 -v '3.16.14.19' -- --with-system-v8
# 3. Install therubyracer using the v8 binary we just installed
$ gem install therubyracer -- --with-v8-dir=/usr/local/opt/v8@315 # your path could be different, e.g. /usr/local/opt/[email protected]
# 4. Install the remaining dependencies