This will sound a little airy fairy but bare with me please.

Basically, I need a way to specify some source files (directories)/string import files (directories) that will propagate to both ends of the dependency tree.
App depends on LibA and LibB.
LibA specifies source files to propagate.
LibB depends on LibC.

LibC and LibB will both be recompiled with the progregated files from LibA.
App will also be compiled with the source files from LibA.