add_platform_option (Gem::VersionOption)

    # File lib/rubygems/version_option.rb, line 13
      def add_platform_option(task = command, *wrap)
        OptionParser.accept Gem::Platform do |value|
          if value == Gem::Platform::RUBY then
            value
          else
            Gem::Platform.new value
          end
        end

        add_option('--platform PLATFORM', Gem::Platform,
                   "Specify the platform of gem to #{task}", *wrap) do
                     |value, options|
          unless options[:added_platform] then
            Gem.platforms = [Gem::Platform::RUBY]
            options[:added_platform] = true
          end

          Gem.platforms << value unless Gem.platforms.include? value
        end
      end