Merge pull request #24775 from opencv-pushbot:gitee/alalek/build_python2_disable_by_default

cmake/OpenCVDetectPython.cmake

@@ -268,13 +268,19 @@ if(OPENCV_PYTHON_SKIP_DETECTION)
   return()
 endif()
 
-find_python("" "${MIN_VER_PYTHON2}" PYTHON2_LIBRARY PYTHON2_INCLUDE_DIR
+ocv_check_environment_variables(OPENCV_ENABLE_PYTHON2)
+ocv_check_environment_variables(PYTHON2_EXECUTABLE)
+if((OPENCV_ENABLE_PYTHON2 OR PYTHON2_EXECUTABLE OR BUILD_opencv_python2)
+    AND NOT OPENCV_PYTHON2_SKIP_DETECTION
+)
+  find_python("" "${MIN_VER_PYTHON2}" PYTHON2_LIBRARY PYTHON2_INCLUDE_DIR
     PYTHON2INTERP_FOUND PYTHON2_EXECUTABLE PYTHON2_VERSION_STRING
     PYTHON2_VERSION_MAJOR PYTHON2_VERSION_MINOR PYTHON2LIBS_FOUND
     PYTHON2LIBS_VERSION_STRING PYTHON2_LIBRARIES PYTHON2_LIBRARY
     PYTHON2_DEBUG_LIBRARIES PYTHON2_LIBRARY_DEBUG PYTHON2_INCLUDE_PATH
     PYTHON2_INCLUDE_DIR PYTHON2_INCLUDE_DIR2 PYTHON2_PACKAGES_PATH
     PYTHON2_NUMPY_INCLUDE_DIRS PYTHON2_NUMPY_VERSION)
+endif()
 
 option(OPENCV_PYTHON3_VERSION "Python3 version" "")
 find_python("${OPENCV_PYTHON3_VERSION}" "${MIN_VER_PYTHON3}" PYTHON3_LIBRARY PYTHON3_INCLUDE_DIR