Add opencv_contrib support and configure extra modules path in CMakeLists.txt

cross_compile/vendor_packages/opencv_vendor/CMakeLists.txt

@@ -20,6 +20,22 @@ FetchContent_Declare(
   URL https://github.com/opencv/opencv/archive/refs/tags/4.12.0.tar.gz
 )
 
+FetchContent_Declare(
+  opencv_contrib
+  URL https://github.com/opencv/opencv_contrib/archive/refs/tags/4.12.0.tar.gz
+)
+
+# 先单独 populate contrib：只解压，不当子工程 configure（它根目录没有 CMakeLists.txt）
+FetchContent_GetProperties(opencv_contrib)
+if(NOT opencv_contrib_POPULATED)
+  FetchContent_Populate(opencv_contrib)
+endif()
+
+# 必须是 CACHE PATH，且要在 MakeAvailable(opencv) 之前设
+set(OPENCV_EXTRA_MODULES_PATH "${opencv_contrib_SOURCE_DIR}/modules"
+    CACHE PATH "" FORCE)
+
+
 set(WITH_ADE OFF)
 set(WITH_GTK OFF)
 set(WITH_ITT OFF)