Macos deterministic builds

[alexandru0-dev]

karabiner-driverkit uses sw_vers command at runtime for macos which leads to not being reproducible.
This is problematic also for tools like nix. (see relevant comment)

Proposed solution

A proposed solution would be using feature flags
An example would be using driverkit by default (macos version > 10) and usable with (macos version <= 10) building with --no-default-features --features karabiner_kext for example

If you have any ideas do not mind sharing them

Draft kanata diff
Draft karabiner_driverkit diff