From: Michael Hofmann on
gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/2375#note_1321...
iiuc, nproc is coreutils -> gnulib ->
https://github.com/coreutils/gnulib/blob/master/lib/nproc.c, which doesn't
seem to know anything about these newfangled things like cgroups v1/v2