Send archive options via pipe in chrootarchive

After finding our initial thinking on env. space versus arg list space
was wrong, we need to solve this by using a pipe between the caller and
child to marshall the (potentially very large) options array to the
archiver.

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)