I don\'t manage to install therubyracer gem on Yosemite 10.10.
Here is the log:
11:53 $ gem install libv8 -v \'3.16.14.3\' -- --with-system-v8 Building
this happens due to some conflicts with the libv8 as well, although you can just assign a version to the rubyracer and it will be installed:
change the following in the gemfile:
gem 'therubyracer', '~> 0.12.1'
and do bundle install