cmake: fix WITH_VTK usage

'WITH_' variables is intended to enable CMake scripts with some autodetection logic.
'WITH_' can be off, but components is really enabled via command-line options
with proper variables setup (including 'HAVE_').

CMakeLists.txt

@@ -656,7 +656,9 @@ if(WITH_MATLAB)
   include(cmake/OpenCVFindMatlab.cmake)
 endif()
 
-include(cmake/OpenCVDetectVTK.cmake)
+if(WITH_VTK)
+  include(cmake/OpenCVDetectVTK.cmake)
+endif()
 
 if(WITH_OPENVX)
   include(cmake/FindOpenVX.cmake)

cmake/OpenCVDetectVTK.cmake

-if(NOT WITH_VTK)
-  return()
-endif()
-
 # VTK 6.x components
 find_package(VTK QUIET COMPONENTS vtkInteractionStyle vtkRenderingLOD vtkIOPLY vtkFiltersTexture vtkRenderingFreeType vtkIOExport NO_MODULE)
 IF(VTK_FOUND)

modules/viz/CMakeLists.txt

-if(NOT WITH_VTK OR NOT DEFINED HAVE_VTK OR NOT HAVE_VTK)
+if(NOT HAVE_VTK)
   ocv_module_disable(viz)
 endif()