When you have an XCode project and you want it to depend on another project (say because you want to depend on the output binary), just drag the project file in from the finder and setup the Target and Binary dependencies so it looks like this:
Drag in the subproject into your main project folder
Then select your project -> Build phases to add the Target Dependencies
Then add the Link Binary with Libraries
Now your project will build with the subproject and always get the latest binary.