sudo /opt/jruby/bin/jruby -S gem install ruby-gpio
Fetching: concurrent-ruby-0.8.0-java.gem (100%)
NotImplementedError: waitpid unsupported or native support failed to load
                       flock at org/jruby/RubyFile.java:298
  block in cache_update_path at /opt/jruby/lib/ruby/stdlib/rubygems/remote_fetcher.rb:310
                        open at org/jruby/RubyIO.java:1126
                        open at org/jruby/RubyKernel.java:336
           cache_update_path at /opt/jruby/lib/ruby/stdlib/rubygems/remote_fetcher.rb:309
                    download at /opt/jruby/lib/ruby/stdlib/rubygems/remote_fetcher.rb:168
                    download at /opt/jruby/lib/ruby/stdlib/rubygems/source.rb:210
                    download at /opt/jruby/lib/ruby/stdlib/rubygems/resolver/activation_request.rb:60
            block in install at /opt/jruby/lib/ruby/stdlib/rubygems/request_set.rb:160
                        each at org/jruby/RubyArray.java:1571
                     install at /opt/jruby/lib/ruby/stdlib/rubygems/request_set.rb:150
                 install_gem at /opt/jruby/lib/ruby/stdlib/rubygems/commands/install_command.rb:249
       block in install_gems at /opt/jruby/lib/ruby/stdlib/rubygems/commands/install_command.rb:299
                        each at org/jruby/RubyArray.java:1571
                install_gems at /opt/jruby/lib/ruby/stdlib/rubygems/commands/install_command.rb:295
                     execute at /opt/jruby/lib/ruby/stdlib/rubygems/commands/install_command.rb:202
      invoke_with_build_args at /opt/jruby/lib/ruby/stdlib/rubygems/command.rb:307
                process_args at /opt/jruby/lib/ruby/stdlib/rubygems/command_manager.rb:168
                         run at /opt/jruby/lib/ruby/stdlib/rubygems/command_manager.rb:138
                         run at /opt/jruby/lib/ruby/stdlib/rubygems/gem_runner.rb:54
                       <top> at /opt/jruby/bin/jgem:21
                        load at org/jruby/RubyKernel.java:984
                       <top> at /opt/jruby/bin/gem:4