When flashing with west flash, we were passing --runner nrfjprog to it, which would fail if the board did not support the nrfjprog runner.
To be more flexible, we are now reading the runners.yaml file to check that we're using the nrfjprog runner, and only pass nrfjprog specific arguments if we are. In other scenarios, we will only try passing the standardized arguments for serial number and erase.