title: I am getting this gem install error for kgio gem when i do a bundle install
body: <p>I added unicorn to my Gemfile and after that when i do a bundle install I get this error</p>
  
  <pre><code>    em::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
  
          /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/bin/ruby extconf.rb 
  checking for CLOCK_MONOTONIC in time.h... *** extconf.rb failed ***
  Could not create Makefile due to some reason, probably lack of
  necessary libraries and/or headers.  Check the mkmf.log file for more
  details.  You may need configuration options.
  
  Provided configuration options:
      --with-opt-dir
      --with-opt-include
      --without-opt-include=${opt-dir}/include
      --with-opt-lib
      --without-opt-lib=${opt-dir}/lib
      --with-make-prog
      --without-make-prog
      --srcdir=.
      --curdir
      --ruby=/Users/adim86/.rvm/rubies/ruby-1.9.3-p0/bin/ruby
  /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
  You have to install development tools first.
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:491:in `block in try_compile'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:443:in `with_werror'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:491:in `try_compile'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:686:in `macro_defined?'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:822:in `block in have_macro'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:254:in `open'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:254:in `open'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
      from /Users/adim86/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/mkmf.rb:821:in `have_macro'
      from extconf.rb:5:in `&lt;main&gt;'
  
  
  Gem files will remain installed in /Users/adim86/.rvm/gems/ruby-1.9.3-p0/gems/kgio-2.7.4 for inspection.
  Results logged to /Users/adim86/.rvm/gems/ruby-1.9.3-p0/gems/kgio-2.7.4/ext/kgio/gem_make.out
  An error occured while installing kgio (2.7.4), and Bundler cannot continue.
  Make sure that `gem install kgio -v '2.7.4'` succeeds before bundling
  </code></pre>
  
  <p>My gem file looks like this. I have tried adding unicorn to a production block but i still get the same error. I have also removed unicorn and i still get the same error also tried a bundle update to no avail:</p>
  
  <pre><code>source 'https://rubygems.org'
  
  gem 'rails', '3.2.3'
  
  gem 'devise'
  gem 'haml-rails'
  
  gem 'omniauth'
  gem 'omniauth-twitter'
  gem 'omniauth-facebook'
  gem 'twitter'
  gem 'fb_graph'
  
  gem 'json'
  gem 'json_pure'
  
  gem 'simple_form'
  gem 'postmark'
  gem 'postmark-rails'
  
  gem 'bootstrap-datepicker-rails'
  gem 'watu_table_builder', :require =&gt; 'table_builder'
  
  gem 'sqlite3'
  
  # Gems used only for assets and not required
  # in production environments by default.
  group :assets do
    gem 'uglifier', '&gt;= 1.0.3'
  end
  
  gem "therubyracer", :require =&gt; 'v8'
  
  gem 'jquery-rails'
  
  gem 'differ'
  
  
  gem 'whenever'
  gem 'unicorn'
  </code></pre>
  
  <p>can anyone help?</p>