This is how I set up the cmake, in the root of OpenCV 4.9.0. repository:

cmake -DCMAKE_ANDROID_NDK=D:...libAndroidSDKndk25.1.8937393 
 -DCMAKE_SYSTEM_NAME=Android 
 -B..OpenCV_4.9.0_buildsandroid_clang_ndk25 -S. 
 -DANDROID_TOOLCHAIN=clang++ 
 -DANDROID_ABI=arm64-v8a 
 -D CMAKE_BUILD_TYPE=Release 
 -D ANDROID_NATIVE_API_LEVEL=24 
 -D WITH_CUDA=OFF 
 -D WITH_MATLAB=OFF 
 -D BUILD_ANDROID_EXAMPLES=OFF 
 -D BUILD_DOCS=OFF 
 -D BUILD_PERF_TESTS=OFF 
 -D BUILD_TESTS=OFF 
 -D ANDROID_STL=c++_shared 
 -D BUILD_SHARED_LIBS=ON

But when I then try to go to android_clang_ndk25, I can see it still uses mingw header files and mingw linker.

I compile with:

D:...ndk21.1.6352462prebuiltwindows-x86_64binmake.exe install

And get errors:

ld: error: undefined symbol: std::__once_callable
>>> referenced by C:/Qt/Tools/mingw1120_64/lib/gcc/x86_64-w64-mingw32/11.2.0/include/c++/mutex:710
>>>               objects.a(caffe_importer.cpp.obj):(cv::dnn::dnn4_v20231225::(anonymous namespace)::CaffeImporter::extractLayerParams(google::protobuf::Message const&, cv::dnn::dnn4_v20231225::LayerParams&, bool))
>>> referenced by C:/Qt/Tools/mingw1120_64/lib/gcc/x86_64-w64-mingw32/11.2.0/include/c++/mutex:718
>>>               objects.a(caffe_importer.cpp.obj):(cv::dnn::dnn4_v20231225::(anonymous namespace)::CaffeImporter::extractLayerParams(google::protobuf::Message const&, cv::dnn::dnn4_v20231225::LayerParams&, bool))
>>> referenced by C:/Qt/Tools/mingw1120_64/lib/gcc/x86_64-w64-mingw32/11.2.0/include/c++/mutex:710
>>>               objects.a(caffe_importer.cpp.obj):(cv::dnn::dnn4_v20231225::(anonymous namespace)::CaffeImporter::extractLayerParams(google::protobuf::Message const&, cv::dnn::dnn4_v20231225::LayerParams&, bool))
>>> referenced 1093 more times

ld: error: undefined symbol: std::__once_call
>>> referenced by C:/Qt/Tools/mingw1120_64/lib/gcc/x86_64-w64-mingw32/11.2.0/include/c++/mutex:712
>>>               objects.a(caffe_importer.cpp.obj):(cv::dnn::dnn4_v20231225::(anonymous namespace)::CaffeImporter::extractLayerParams(google::protobuf::Message const&, cv::dnn::dnn4_v20231225::LayerParams&, bool))
>>> referenced by C:/Qt/Tools/mingw1120_64/lib/gcc/x86_64-w64-mingw32/11.2.0/include/c++/mutex:719
>>>               objects.a(caffe_importer.cpp.obj):(cv::dnn::dnn4_v20231225::(anonymous namespace)::CaffeImporter::extractLayerParams(google::protobuf::Message const&, cv::dnn::dnn4_v20231225::LayerParams&, bool))
>>> referenced by C:/Qt/Tools/mingw1120_64/lib/gcc/x86_64-w64-mingw32/11.2.0/include/c++/mutex:712
>>>               objects.a(caffe_importer.cpp.obj):(cv::dnn::dnn4_v20231225::(anonymous namespace)::CaffeImporter::extractLayerParams(google::protobuf::Message const&, cv::dnn::dnn4_v20231225::LayerParams&, bool))
>>> referenced 1082 more times
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [modulesdnnCMakeFilesopencv_dnn.dirbuild.make:2858: bin/libopencv_dnn490.dll] Error 1
make[1]: *** [CMakeFilesMakefile2:1870: modules/dnn/CMakeFiles/opencv_dnn.dir/all] Error 2
make: *** [Makefile:165: all] Error 2

Notably, it also says after configuring it is using MinGW:

-- General configuration for OpenCV 4.9.0 =====================================
--   Version control:               4.9.0
--
--   Platform:
--     Timestamp:                   2024-04-08T09:17:02Z
--     Host:                        Windows 10.0.19045 AMD64
--     CMake:                       3.25.2
--     CMake generator:             MinGW Makefiles
--     CMake build tool:            C:/Qt/Tools/mingw1120_64/bin/mingw32-make.exe
--     Configuration:               Release