which copies the init stuff (whatever it is) from store to /persist
instead of making liminix-rebuild have to know what the files are.
This is principally to ease making a system configuration in /mnt or
similar when operating in a rescue/recovery scenario, and we
don't want to liminix-rebuild because it will reboot
this is step 1 of min-collect-garbage, no point implementing
deletion ourselves when rm -r exists
(arguably no point in implementing any of it, but this is the bit we
can't do efficiently in bourne shell - it means we're reading the
store-paths list once instead of grepping it afresh for every entry in
/nix/store/)
