VTKCompatibility: ignore for "modern" VTK

Modern versions which use the module system really don't need any of the
hacks needed here.

Modules/VTKCompatibility.cmake

 # Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
 # file Copyright.txt or https://cmake.org/licensing for details.
 
+# Not needed for "modern" VTK.
+if (EXISTS "${VTK_SOURCE_DIR}/CMake/vtkModule.cmake")
+  return ()
+endif ()
 
 if(APPLE)
   set(CMAKE_CXX_CREATE_SHARED_LIBRARY "${CMAKE_C_CREATE_SHARED_LIBRARY}")