Merge pull request #30040 from vrabaud:function_ptr

Fix function pointer signature mismatches - #30040

Contrib PR: https://github.com/opencv/opencv_contrib/pull/4224

Calling a function through a function pointer with a mismatched signature is undefined behavior in C/C++ and causes Clang Control Flow Integrity to trap with `SIGILL` (`ud1`) at indirect call sites.

This is a follow-up on https://github.com/opencv/opencv/pull/28939

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/python/src2/cv2.cpp

@@ -2,6 +2,14 @@
 // https://numpy.org/doc/1.17/reference/c-api.array.html#importing-the-api
 #define PY_ARRAY_UNIQUE_SYMBOL opencv_ARRAY_API
 
+#if defined(__clang__)
+#pragma clang diagnostic ignored "-Wunknown-warning-option"
+#pragma clang diagnostic ignored "-Wcast-function-type-strict"
+#elif defined(__GNUC__)
+#pragma GCC diagnostic ignored "-Wpragmas"
+#pragma GCC diagnostic ignored "-Wcast-function-type-strict"
+#endif
+
 #include "cv2.hpp"
 
 #include "opencv2/opencv_modules.hpp"