How do I get json gem 1.7.7 to Update? - ruby-on-rails

Question

I'm trying to run a rails app on my Windows 8.1 computer, but I need json gem version 1.8.1. I currently have json 1.7.7. Bundle install returns an error and asks for me to make sure "gem install json -v 1.8.1" succeeds. Running that command returns
E:\rails_projects\bookit>gem install json -v 1.8.2
Temporarily enhancing PATH to include DevKit...
Building native extensions. This could take a while...
ERROR: Error installing json:
ERROR: Failed to build gem native extension.
C:/Ruby200-x64/bin/ruby.exe -r ./siteconf20150212-3852-vjuo23.rb extconf.rb
creating Makefile
make "DESTDIR=" clean
make "DESTDIR="
generating generator-x64-mingw32.def
compiling generator.c
make: x86_64-w64-mingw32-gcc: Command not found
make: *** [generator.o] Error 127
make failed, exit code 2
Gem files will remain installed in C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/json-
1.8.2 for inspection.
Results logged to C:/Ruby200-x64/lib/ruby/gems/2.0.0/extensions/x64-mingw32/2.0.
0/json-1.8.2/gem_make.out
E:\rails_projects\bookit>
I added the DevKit path to my list of environment variables. I find it odd that I am having a problem with DevKit because green_shoes installs and works fine, and it requires DevKit. What am I missing?
Note:
I am using Ruby 2.0.0, 64-bit, as well as the corresponding DevKit as recommended by rubyinstaller.org
EDIT: Gemfile for my rails app
source 'https://rubygems.org'
ruby '2.0.0'
gem 'rails', '4.1.4'
gem 'bootstrap-sass', '2.3.2.0'
gem 'sprockets', '2.11.0'
gem 'bcrypt-ruby', '3.1.2'
gem 'will_paginate', '3.0.4'
gem 'bootstrap-will_paginate', '0.0.9'
gem 'barista'
gem 'jquery-rails'
group :development, :test do
gem 'sqlite3'
gem 'rspec-rails', '2.14.0'
end
group :test do
gem 'selenium-webdriver', '2.35.1'
gem 'capybara', '2.1.0'
gem 'factory_girl_rails', '4.2.0'
end
gem 'sass-rails', '~> 4.0.3'
gem 'uglifier', '>= 1.3.0'
gem 'coffee-rails', '~> 4.0.0'
gem 'jquery-rails'
https://github.com/rails/turbolinks
gem 'turbolinks'
gem 'jbuilder', '~> 2.0'
group :doc do
gem 'sdoc', '~> 0.4.0', require: false
end
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw]
group :production do
gem 'pg', '0.15.1'
gem 'rails_12factor', '0.0.2'
end

Answer 1

This is your error:
make: x86_64-w64-mingw32-gcc: Command not found
--
The error is caused because the gcc/gc++ compiler is not found on your computer.
You should refer to this page for more information on this.
You should download this build kit, install it and then run the following:
set PATH=c:/path/to/your/mingw64/installation;%PATH%
Then perform the build again - it should work.