firstDll
    Core.start("first")
secondDll
    core.start("second")

Core(lib)
    void start()
    if "first" compiled :
    #include "firstAddOn\macros.h"
    else if "Second" compiled :
    #include "secondAddOn\macros.h"


firstAddOn(lib)
    macros.h

secondAddOn(lib)
    macros.h