message: fix find_package cache pollution
diff: -# VTK 9.0
  if(NOT VTK_FOUND)
  + find_package(VTK QUIET NAMES vtk VTK)
  + if(VTK_FOUND)
  + if(VTK_VERSION VERSION_EQUAL "9") # VTK 9.0
  find_package(VTK 9 QUIET NAMES vtk COMPONENTS
  FiltersExtraction
  FiltersSources
  @@ -12,10 +14,7 @@ if(NOT VTK_FOUND)
  RenderingLOD
  RenderingOpenGL2
  NO_MODULE)
  -endif()
  -
  -# VTK 6.x components
  -if(NOT VTK_FOUND)
  + elseif(VTK_VERSION VERSION_GREATER "5") # VTK 6.x components
  find_package(VTK QUIET COMPONENTS vtkInteractionStyle vtkRenderingLOD vtkIOPLY vtkFiltersTexture vtkRenderingFreeType vtkIOExport NO_MODULE)
  IF(VTK_FOUND)
  IF(VTK_RENDERING_BACKEND) #in vtk 7, the rendering backend is exported as a var.
  @@ -24,11 +23,12 @@ if(NOT VTK_FOUND)
  find_package(VTK QUIET COMPONENTS vtkRenderingOpenGL vtkInteractionStyle vtkRenderingLOD vtkIOPLY vtkFiltersTexture vtkRenderingFreeType vtkIOExport NO_MODULE)
  ENDIF(VTK_RENDERING_BACKEND)
  ENDIF(VTK_FOUND)
  -endif()
  -
  -# VTK 5.x components
  -if(NOT VTK_FOUND)
  + elseif(VTK_VERSION VERSION_EQUAL "5") # VTK 5.x components
  find_package(VTK QUIET COMPONENTS vtkCommon NO_MODULE)
  + else()
  + set(VTK_FOUND FALSE)
  + endif()
  + endif()
  endif()
  if(NOT VTK_FOUND)
  