[CMake] Consistent software dependencies (together with add_subdirectory()?) for shared components

[SF Markus Elfring]

Hello,

CMake provides an interface for the addition of subdirectories.
https://cmake.org/cmake/help/v3.9/command/add_subdirectory.html

I find it interesting to clarify details which are not described there so far.

* How much does this item influence the capability to construct a consistent
  dependency graph for the generated build system also around shared
  software components in several folders?

* Can it mean a barrier for advanced data exchange with build configuration
  information between shared components?

Regards,
Markus