# File lib/bundler/rubygems_integration.rb, line 822
      def backport_ext_builder_monitor
        # So we can avoid requiring "rubygems/ext" in its entirety
        Gem.module_eval "module Ext\nend\n", __FILE__, __LINE__ + 1

        require "rubygems/ext/builder"

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

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