system(syscall): switch to x/sys

[gen2thomas]

Solved issues and/or description of the change

• syscall package is locked down - need switch to x/sys/unix #895
• importas linter deactivated
• Makefile adjusted to fail fast on tests

If needed, a windows syscall (syscall_windows.go) can now be implemented without affecting the driver code. This is not done yet, because we use syscall for I2C drivers only and depend on Linux Kernel.

Manual test

• Linux: armbian
• Adaptor(s) and/or driver(s): Tinkerboard with PCA9533 (i2c test)

Checklist

• The PR's target branch is 'hybridgroup:dev'
• New and existing unit tests pass locally with my changes (e.g. by run make test)
• No linter errors exist locally (e.g. by run make fmt_check)
• I have performed a self-review of my own code

[gen2thomas]

Going to merge without further review, because all tests passed and a manual test for i2c is working.