warning: unused argument during compilation

Started getting this warning after moving to Ubuntu 20.04.

Using RX Vega 64 and the AMD gpupro drivers. My Kernel executes and runs fine, but having the warning pop up is frustrating. Is it possible to resolve this? Or suppress the warning completely. Setting `os.environ[ "PYOPENCL_COMPILER_OUTPUT" ] = "0"` still displays a warning.

```
/home/jer/python/virtualenv/REDHOT4/lib/python3.8/site-packages/pyopencl/__init__.py:264: CompilerWarning: Built kernel retrieved from cache. Original from-source build had warnings:
Build on succeeded, but said:

warning: argument unused during compilation: '-I /home/jer/python/virtualenv/REDHOT4/lib/python3.8/site-packages/pyopencl/cl'
1 warning generated.

warn(text, CompilerWarning)
```