# File lib/bundler/rubygems_integration.rb, line 622
      def backport_ext_builder_monitor
        require 'rubygems/ext'

        Gem::Ext::Builder.class_eval do
          if !const_defined?(:CHDIR_MONITOR)
            const_set(:CHDIR_MONITOR, EXT_LOCK)
          end

          if const_defined?(:CHDIR_MUTEX)
            remove_const(:CHDIR_MUTEX)
          end
          const_set(:CHDIR_MUTEX, const_get(:CHDIR_MONITOR))
        end
      end