install_gem.rb

      def run
        command = "gem install #{gemspec_helper.gem_path}"
        output.puts "Executing #{command.inspect}:"
        sh sudo(command)
      end

      def sudo(command)
        "#{'sudo ' if use_sudo?}#{command}"
      end

      def use_sudo?
        !(Config::CONFIG['host_os'] =~ /mswin|windows|cygwin/i)        
      end