title: Gem::Ext::BuildError: ERROR: Failed to build gem native extension. - CentOS 6.5
body: <p>I'm trying to get Ruby version 2.0.0-p353 to run on Nginx 1.4.7 on CentOS 6.5. Everything installs as expected, but when I get to the point of running <code>bundle install</code> I get the following error:</p>
  
  <p>Gem::Ext::BuildError: ERROR: Failed to build gem native extension.</p>
  
  <pre><code>/usr/local/rvm/rubies/ruby-2.0.0-p353/bin/ruby extconf.rb 
  checking for pg_config... no
  No pg_config... trying anyway. If building fails, please try again with
   --with-pg-config=/path/to/pg_config
  checking for libpq-fe.h... no
  Can't find the 'libpq-fe.h header
  *** 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
          --without-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=/usr/local/rvm/rubies/ruby-2.0.0-p353/bin/ruby
          --with-pg
          --without-pg
          --with-pg-config
          --without-pg-config
          --with-pg_config
          --without-pg_config
          --with-pg-dir
          --without-pg-dir
          --with-pg-include
          --without-pg-include=${pg-dir}/include
          --with-pg-lib
          --without-pg-lib=${pg-dir}/
  
  extconf failed, exit code 1
  
  Gem files will remain installed in /root/.rvm/gems/ruby-2.0.0-p353@rails4/gems/pg-0.17.1 for inspection.
  Results logged to /root/.rvm/gems/ruby-2.0.0-p353@rails4/extensions/x86_64-linux/2.0.0/pg-0.17.1/gem_make.out
  An error occurred while installing pg (0.17.1), and Bundler cannot continue.
  Make sure that `gem install pg -v '0.17.1'` succeeds before bundling.
  </code></pre>
  
  <p>I couldn't locate the mkmf.log file mentioned.</p>