Install libv8 and therubyracer on windows

libv8

1. You can find the PATH variable in Windows in Control Panel -> System -> Advanced System Configuration -> Environment Variables.

My PATH variable is: C:\Ruby192\bin;C:\Python27

In a Command Prompt with Ruby, you can set the variable for that console using the command

SET PATH=C:\Ruby192\bin;C:\Python27

You can check the values using the command

PATH

Then, install gem as usual: gem install libv8

OR


2. 
In your Gemfile isolate the TheRubyRacer gem to the production environment like this:

group :production do
  gem 'therubyracer-heroku', :platform => :ruby
end
In your development environment, instead of a plain bundle install do

bundle install --without production
or, as Nik suggests, bundle install development. When you deploy to Heroku it will install the gem because it is the production environment
Hope this helps