- Update to 1.8.1:
https://github.com/liquidctl/liquidctl/releases/tag/v1.8.1
https://github.com/liquidctl/liquidctl/releases/tag/v1.8.0
https://github.com/liquidctl/liquidctl/releases/tag/v1.7.2
https://github.com/liquidctl/liquidctl/releases/tag/v1.7.1
https://github.com/liquidctl/liquidctl/releases/tag/v1.7.0

- modernize the spec file a bit
- use python3 macros
- install -D to save one line:p
- add easy way to test if all dependencies are available at build
time