pbx/Makefile: Revert r423237

This patch was supposed to go into a team branch, but I was a bit fast on the
gun before 'svn switch' had apparently moved the target branch over.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@423238 65c4cc65-6c06-0410-ace0-fbb531ad65f3