Setup consists of:
- LinkerTester application
- appdelegate
- provides class B
- libA
- provides class A
- uses class B from libB
- libB
- provides class B (different class than in LinkerTester application)
LinkerTester links to libA. libA uses libB but doesn't wants its clients to know it. So it manually hides all its symbols besides class A via manually exporting its symbols.