Merge pull request #25832 from chachoi-world:4.x

Add support for QNX #25832

Build and test instruction for QNX:
https://github.com/chachoi-world/qnx-ports/blob/main/opencv/README.md

### 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
- [ ] 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/core/include/opencv2/core/utils/filesystem.private.hpp

@@ -13,7 +13,7 @@
      /* not supported */
 #  elif defined __ANDROID__ || defined __linux__ || defined _WIN32 || \
         defined __FreeBSD__ || defined __bsdi__ || defined __HAIKU__ || \
-        defined __GNU__
+        defined __GNU__ || defined __QNX__
 #      define OPENCV_HAVE_FILESYSTEM_SUPPORT 1
 #  elif defined(__APPLE__)
 #    include <TargetConditionals.h>