MFC r245825,245890,246097,246127,246315:

Introduce a new option -DNO_ROOT that allows install and distribution
targets to be run without root privilege.

Information about ownership, group, flags, and suid bits are stored in
the file specified by METALOG which defaults to ${DESTDIR}/METALOG.
This file can be used in conjunction with bsdtar or makefs to generate
archives or file system images with correct permissions.

Sponsored by:	DARPA, AFRL