samples: update parallel_backend examples

- use find_package(TBB)

samples/cpp/CMakeLists.txt

@@ -72,6 +72,8 @@ include("tutorial_code/calib3d/real_time_pose_estimation/CMakeLists.txt" OPTIONA
 if(OpenCV_FOUND AND NOT CMAKE_VERSION VERSION_LESS "3.1")
   add_subdirectory("example_cmake")
 endif()
-if(OpenCV_FOUND AND NOT CMAKE_VERSION VERSION_LESS "3.9")
+if(OpenCV_FOUND AND NOT CMAKE_VERSION VERSION_LESS "3.9"
+    AND NOT OPENCV_EXAMPLES_SKIP_PARALLEL_BACKEND
+)
   add_subdirectory("tutorial_code/core/parallel_backend")
 endif()

samples/cpp/tutorial_code/core/parallel_backend/CMakeLists.txt

@@ -2,6 +2,9 @@ cmake_minimum_required(VERSION 3.9)
 
 find_package(OpenCV REQUIRED COMPONENTS opencv_core)
 
+if(NOT OPENCV_EXAMPLES_SKIP_PARALLEL_BACKEND_OPENMP
+    AND NOT OPENCV_EXAMPLES_SKIP_OPENMP
+)
   find_package(OpenMP)
   if(OpenMP_FOUND)
     project(opencv_example_openmp_backend)
@@ -11,11 +14,18 @@ if(OpenMP_FOUND)
         OpenMP::OpenMP_CXX
     )
   endif()
+endif()
 
-# TODO: find_package(TBB)
+if(NOT OPENCV_EXAMPLES_SKIP_PARALLEL_BACKEND_TBB
+    AND NOT OPENCV_EXAMPLES_SKIP_TBB
+    AND NOT OPENCV_EXAMPLE_SKIP_TBB  # deprecated (to be removed in OpenCV 5.0)
+)
+  find_package(TBB)
+  if(NOT TBB_FOUND)
     find_path(TBB_INCLUDE_DIR NAMES "tbb/tbb.h")
     find_library(TBB_LIBRARY NAMES "tbb")
-if(TBB_INCLUDE_DIR AND TBB_LIBRARY AND NOT OPENCV_EXAMPLE_SKIP_TBB)
+  endif()
+  if(TBB_INCLUDE_DIR AND TBB_LIBRARY)
     project(opencv_example_tbb_backend)
     add_executable(opencv_example_tbb_backend example-tbb.cpp)
     target_include_directories(opencv_example_tbb_backend SYSTEM PRIVATE ${TBB_INCLUDE_DIR})
@@ -24,3 +34,4 @@ if(TBB_INCLUDE_DIR AND TBB_LIBRARY AND NOT OPENCV_EXAMPLE_SKIP_TBB)
         ${TBB_LIBRARY}
     )
   endif()
+endif()