message: cmake: allow to disable ADE build too (BUILD_opencv_gapi=OFF is not enough)
  CMake option: WITH_ADE=OFF
diff: +OCV_OPTION(WITH_ADE "Enable ADE framework (required for Graph API module)" ON)
  +
  +if(NOT WITH_ADE)
  + return()
  +endif()
  +
  if (ade_DIR)
  # if ade_DIR is set, use ADE-supplied CMake script
  # to set up variables to the prebuilt ADE
  