Nonterminating build process if inheritance relation is cyclic

[RolandKluge]

How to reproduce:

• Do the eMoflon::Core tutorial until you arrive at creating the inheritance relations.
• Use the following metamodel.
• The build process does not terminate.

  
  @GenModel(documentation="TODO: Add documentation for Blup")
  @namespace(uri="platform:/plugin/SokobanLanguage/model/SokobanLanguage.ecore", prefix="SokobanLanguage")
  package SokobanLanguage;

class Block extends Boulder {

}

class Board {

}

class Boulder {

}

class Figure extends Figure {

}

class Sokoban extends Figure {

}