With powerd_flags="-N", this makes powerd(8) exclude "nice" time when
computing the CPU utilization. This makes it possible to prevent
CPU-intensive "background" processes from spinning up the CPU.
Note that only *userland* CPU usage belonging to "nice" processes is
excluded; we do not track whether time spent in the kernel is on behalf
of nice or non-nice processes, so kernel-intensive nice processes can
still result in the CPU being sped up.