Fix OpenCV include layout across platforms

Author: allnes

cmake/opencv_config.cmake

@@ -138,7 +138,10 @@ set(OPENCV_LIBRARY_DIR
     "${OPENCV_INSTALL_DIR}/${OPENCV_INSTALL_BINARIES_PREFIX}${CMAKE_INSTALL_LIBDIR}")
 set(OPENCV_RUNTIME_DIR
     "${OPENCV_INSTALL_DIR}/${OPENCV_INSTALL_BINARIES_PREFIX}${CMAKE_INSTALL_BINDIR}")
-set(OPENCV_INCLUDE_DIR "${OPENCV_INSTALL_DIR}/include/opencv4")
+set(OPENCV_INCLUDE_DIRS
+    "${OPENCV_INSTALL_DIR}/include"
+    "${OPENCV_INSTALL_DIR}/include/opencv4"
+)
 
 if(WIN32)
     set(OPENCV_WORLD_IMPLIB
@@ -173,7 +176,7 @@ add_library(opencv_world_external SHARED IMPORTED GLOBAL)
 add_dependencies(opencv_world_external opencv_external)
 set_target_properties(opencv_world_external PROPERTIES
     IMPORTED_LOCATION "${OPENCV_WORLD_RUNTIME}"
-    INTERFACE_INCLUDE_DIRECTORIES "${OPENCV_INCLUDE_DIR}"
+    INTERFACE_INCLUDE_DIRECTORIES "${OPENCV_INCLUDE_DIRS}"
 )
 
 if(WIN32)
@@ -184,7 +187,7 @@ endif()
 
 add_library(OpenCV_unified INTERFACE)
 add_dependencies(OpenCV_unified opencv_external)
-target_include_directories(OpenCV_unified INTERFACE "${OPENCV_INCLUDE_DIR}")
+target_include_directories(OpenCV_unified INTERFACE ${OPENCV_INCLUDE_DIRS})
 target_link_libraries(OpenCV_unified INTERFACE opencv_world_external)
 
 if(CMAKE_BUILD_RPATH)