I did not find how to print logs to Xcode console from lua so I have tried to create a plugin for that job,
Here is a simple iOS plugin to print logs from lua to Xcode.
copy it to your Xcode project's Plugins directory,
local ioslog = require "ioslog"
ioslog.xlog ("Something goes to console")
It is created by following the tutorial from here http://howto.oz-apps.com/2013/11/creating-plug-in-for-lua-framework.html