I am getting an error when trying to install rails (or more specifically, atomic).

```
Building native extensions.  This could take a while... ERROR:  Error installing rails:     ERROR: Failed to build gem native extension.

    /Users/dima/.rvm/rubies/ruby-2.0.0-p247/bin/ruby extconf.rb creating Makefile

make compiling atomic_reference.c atomic_reference.c:50:9: warning: implicit declaration of function 'OSAtomicCompareAndSwap64' is invalid in C99 [-Wimplicit-function-declaration]
    if (OSAtomicCompareAndSwap64(expect_value, new_value, &DATA_PTR(self))) {
        ^ 1 warning generated. linking shared-object atomic_reference.bundle

make install /usr/bin/install -c -m 0755 atomic_reference.bundle /Users/dima/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/atomic-1.1.10/lib/Users/dima/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/site_ruby/2.0.0/x86_64-darwin12.4.0 install: /Users/dima/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/atomic-1.1.10/lib/Users/dima/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/site_ruby/2.0.0/x86_64-darwin12.4.0: No such file or directory make: *** [install-so] Error 71

Gem files will remain installed in /Users/dima/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/atomic-1.1.10 for inspection. Results logged to /Users/dima/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/atomic-1.1.10/ext/gem_make.out

```

I'm basically just following the rails tutorial (for rails 4.0 and ruby 2.0, [seen here](http://ruby.railstutorial.org/ruby-on-rails-tutorial-book?version=4.0#code-create_gemrc)) and have kind of hit a wall here, unfortunately, unable to find much info on what's happening here.

I found [this question](https://stackoverflow.com/questions/17353088/error-installing-ruby-on-rails-4-0-0-error-compiling-atomic-reference-c) and followed both suggestions in the answer with the same result.