anchor.diff:    # booting (such as the FS containing `/nix/store`, or an FS needed for
     # mounting `/`, like `/` on a loopback).
     fileSystems = filter utils.fsNeededForBoot config.system.build.fileSystems;
  +
  +  # Determine whether zfs-mount(8) is needed.
  +  zfsRequiresMountHelper = any (fs: lib.elem "zfsutil" fs.options) fileSystems;
   
     # A utility for enumerating the shared-library dependencies of a program
     findLibs = pkgs.buildPackages.writeShellScriptBin "find-libs" ''
  
positive.code:       for BIN in ${pkgs.busybox}/{s,}bin/*; do
          copy_bin_and_libs $BIN
        done
  
        # Copy some util-linux stuff.
        copy_bin_and_libs ${pkgs.util-linux}/sbin/blkid
  
negative.code:       echo "testing patched programs..."
        $out/bin/ash -c 'echo hello world' | grep "hello world"
        export LD_LIBRARY_PATH=$out/lib
        ${if zfsRequiresMountHelper then ''
          $out/bin/mount -V 1>&1 | grep -q "mount from util-linux"
          $out/bin/mount.zfs -h 2>&1 | grep -q "Usage: mount.zfs"
        '' else ''
          $out/bin/mount --help 2>&1 | grep -q "BusyBox"
        ''}
        $out/bin/blkid -V 2>&1 | grep -q 'libblkid'
        $out/bin/udevadm --version
        $out/bin/dmsetup --version 2>&1 | tee -a log | grep -q "version:"
  