title: Paperclip with JRuby
body: <p>Recently I was adapting my rails app to run on JRuby.
  One of problems that i've encountered was with Paperclip.
  Paperclip uses Cocaine to run command line tools like ImageMagick and it uses Process.spawn, which results in:</p>
  
  <pre>
  Errno::ECHILD: No child processes - No child processes
                   waitpid at org/jruby/RubyProcess.java:512
                   waitpid at org/jruby/RubyProcess.java:497
                   waitpid at /home/cthulhu/.rvm/gems/jruby-1.6.7.2/gems/cocaine-0.3.0/lib/cocaine/command_line/runners/process_runner.rb:21
                      call at /home/cthulhu/.rvm/gems/jruby-1.6.7.2/gems/cocaine-0.3.0/lib/cocaine/command_line/runners/process_runner.rb:9
                   execute at /home/cthulhu/.rvm/gems/jruby-1.6.7.2/gems/cocaine-0.3.0/lib/cocaine/command_line.rb:77
                       run at /home/cthulhu/.rvm/gems/jruby-1.6.7.2/gems/cocaine-0.3.0/lib/cocaine/command_line.rb:55
                       run at /home/cthulhu/.rvm/gems/jruby-1.6.7.2/gems/paperclip-3.2.0/lib/paperclip/helpers.rb:29
  </pre>
  
  <p>Is there any way to make Paperclip work smoothly with JRuby? I'm running my app on linux only, so i don't mind using linux native tools like ImageMagick.</p>
  
  <p>Rails 3.2.8, JRuby 1.6.7.2</p>