Currently CMake PCH generator doesn't support dependency on auto-generated files (it is actual for Linux platforms).
So please move this include into .cpp files (it is actual for all `precomp.hpp`).

Error log sample:

```
[  3%] Building CXX object modules/core/CMakeFiles/opencv_core_pch_dephelp.dir/opencv_core_pch_dephelp.cxx.o
In file included from /home/buildslave/project/amdocl/buildslave/precommit_OCL-lin64/build/modules/core/opencv_core_pch_dephelp.cxx:1:0:
/home/buildslave/project/amdocl/buildslave/precommit_OCL-lin64/opencv/modules/core/src/precomp.hpp:70:30: fatal error: opencl_kernels.hpp: No such file or directory
compilation terminated.
```