This fixes a regression introduced in
df2f6400b1fbc282ef4d6dd7124ea1c17adc23c2: since the new
'register-path' (actually 'reset-timestamps') would make files
read-only, 'delete-file-recursively' would fail to delete them. Thus,
re-running 'guix system init' on an already-populated store would fail
with a 'delete-file' EPERM.
* guix/scripts/system.scm (copy-item): Use 'lstat' instead of
'file-exists?'. Call 'make-file-writable' on each directory below
DEST.
f3f1d0a557