The author refers to an older version of Xcode, but the settings should be exactly the same.
Tutorial for setting up Xcode to build and compile externals for pd
I've done this a lot in the current Xcode, if anyone's interested I could give some help or show you some sample projects.
Here's a few links to some basic externals that should work:
let me know if they don't work for some reason. Here's a good pdf that goes over more of the details: http://pdstatic.iem.at/externals-HOWTO/pd-externals-HOWTO.pdf