title: Android Navigation Component. How to override fragment or action for another build variant without creating new graph
body: <p>I have 10 flavors(build variants) in gradle and ~50 fragments as Screen.
  As a result nav_graph is very big (~700 lines).
  Extending some fragments is a trivial problem, i have 10% extensions for each build variant</p>
  
  <p>How to override only a fragment or an action for another build variant in order to avoid duplicates?</p>