Merge pull request #25064 from vpisarev:em_5point_fix

Fix very slow compilation of five-point algorithm on some platforms (e.g. Qualcomm) #25064

Thanks to our big friend and long-term contributor for the patch!

### Pull Request Readiness Checklist

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- [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/calib3d/src/five-point.cpp

@@ -36,6 +36,13 @@
 namespace cv
 {
 
+// for some compilers it takes very long time to compile
+// automatically generated code in EMEstimatorCallback::runKernel(),
+// so we temporarily disable optimizations here
+#if defined __hexagon__ && defined __clang__
+#pragma clang optimize off
+#endif
+
 class EMEstimatorCallback CV_FINAL : public PointSetRegistrator::Callback
 {
 public:
@@ -401,6 +408,11 @@ protected:
     }
 };
 
+// restore optimizations (if any)
+#if defined __hexagon__ && defined __clang__
+#pragma clang optimize on
+#endif
+
 // Find essential matrix given undistorted points and two cameras.
 static Mat findEssentialMat_( InputArray _points1, InputArray _points2,
                              InputArray cameraMatrix1, InputArray cameraMatrix2,