Feature request: add Raspberry Pi support
[How to install OpenCL on Raspberry Pi](https://github.com/doe300/VC4CL/wiki/How-to-get)
[Not supported functions](https://github.com/doe300/VC4CL/wiki/NotSupported)
[clinfo output on Pastebin](https://pastebin.com/aQtG1UcT)
xmrig-amd build log:

```
-- Configuring done
CMake Error at CMakeLists.txt:248 (add_executable):
  Cannot find source file:

    src/Cpu_arm.cpp

  Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .hh .h++ .hm .hpp
  .hxx .in .txx


CMake Error: CMake can not determine linker language for target: xmrig-amd
CMake Error: Cannot determine link language for target "xmrig-amd".
-- Generating done
-- Build files have been written to: /home/pi/xmrig/xmrig-amd-master/build
pi@raspberrypi:~/xmrig/xmrig-amd-master/build $ make
make[2]: *** No rule to make target 'CMakeFiles/xmrig-amd.dir/build'.  Stop.
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/xmrig-amd.dir/all' failed
make[1]: *** [CMakeFiles/xmrig-amd.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2
```