Modifying a platform-build

[ItWillDo1]

Hey guys, 

I've managed to download the android-4.4_r1 repo and build it in userdebug configuration and get it working for a hammerhead-device. My problem now is that when I implement my changes, only some of them are applied. I can manage to change the settings by adding an extra menu-fragment but the service that's attached to it doesn't get built, nor does a library that's linked to it. 

Is there a file somewhere where I need to specify these changes and explicitly tell the build-system to make the new library and import it in the final system.img? The library and depending modules are specified in a makefile within the Source directory so I assumed it would trigger the building automatically.