# File lib/jeweler/commands/build_gem.rb, line 10
      def run
        gemspec_helper.update_version(version_helper) unless gemspec_helper.has_version?

        gemspec = gemspec_helper.parse

        require 'rubygems/builder'
        gem_file_name = Gem::Builder.new(gemspec).build

        pkg_dir = File.join(base_dir, 'pkg')
        file_utils.mkdir_p pkg_dir

        gem_file_name = File.join(base_dir, gem_file_name)
        file_utils.mv gem_file_name, pkg_dir
      end