cmake(cuda): update handling of -std=c++11/14 flags

cmake/OpenCVDetectCUDA.cmake

@@ -336,7 +336,14 @@ if(CUDA_FOUND)
     endif()
 
     if(UNIX OR APPLE)
-      set(CUDA_NVCC_FLAGS ${CUDA_NVCC_FLAGS} -Xcompiler -fPIC --std=c++11)
+      set(CUDA_NVCC_FLAGS ${CUDA_NVCC_FLAGS} -Xcompiler -fPIC)
+      if(NOT " ${CMAKE_CXX_FLAGS} ${CMAKE_CXX_FLAGS_RELEASE} ${CMAKE_CXX_FLAGS_DEBUG} ${CUDA_NVCC_FLAGS}" MATCHES "-std=")
+        if(CUDA_VERSION VERSION_LESS "11.0")
+          list(APPEND CUDA_NVCC_FLAGS "--std=c++11")
+        else()
+          list(APPEND CUDA_NVCC_FLAGS "--std=c++14")
+        endif()
+      endif()
     endif()
     if(APPLE)
       set(CUDA_NVCC_FLAGS ${CUDA_NVCC_FLAGS} -Xcompiler -fno-finite-math-only)