CFG: add nodes for block arguments

ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll

@@ -313,13 +313,14 @@ module Trees {
   }
 
   private class CallTree extends StandardPostOrderTree, Call {
-    // this.getBlock() is not included as it uses a different scope
     final override AstNode getChildNode(int i) {
       result = this.getReceiver() and i = 0
       or
       result = this.getMethod() and i = 1
       or
       result = this.getArguments() and i = 2
+      or
+      result = this.getBlock() and i = 3
     }
   }