By default, when you create a new file or import a file into Xcode, if the file type is recognized as a source file (.c, .m .js, etc), the file is added to the Compile Sources folder in the application target.
I achieved this by adding a #define in .pch file for each project.
and do #import based on that definition using #ifdef
This is the pretty cool and easy way if your are sharing single source code set across multiple target/build/project
Just make use of different .pch file for different builds.
You want to create <n> number of .pch file for <n> targets. Assign corresponding .pch file for each target’s info