message: build: fix warning
  C4189: 'clImageUV' : local variable is initialized but not referenced
diff: @@ -794,7 +794,9 @@ void convertToD3D11Texture2D(InputArray src, ID3D11Texture2D* pD3D11Texture2D)
  cl_int status = 0;
  cl_mem clImage = 0;
  +#ifdef HAVE_DIRECTX_NV12
  cl_mem clImageUV = 0;
  +#endif
  clImage = clCreateFromD3D11Texture2DKHR(context, CL_MEM_WRITE_ONLY, pD3D11Texture2D, 0, &status);
  if (status != CL_SUCCESS)
  