installworld with NO_ROOT produces paths with .. for man pages

From: Andriy Gapon <avg_at_FreeBSD.org>
Date: Sat, 28 Aug 2021 14:28:29 UTC
This seems to be related to the recent change to install manual pages for all 
platforms.

My method of creating a cross-platform installation image is to install with 
NO_ROOT and then to tar up with @METALOG argument.
On the destination I simply untar the archive into a destination directory 
(typically a fresh ZFS BE).

Today I noticed some complaints when extracting the archive, here is a few:
./usr/share/man/man4/i386/../smapi.4.gz: Path contains '..'
./usr/share/man/man4/i386/../vpd.4.gz: Path contains '..'
./usr/share/man/man4/powerpc/../adb.4.gz: Path contains '..'
./usr/share/man/man4/powerpc/../akbd.4.gz: Path contains '..'

This is a not a big deal but would be nice to "straighten" the installation 
paths when installing such manual pages.

P.S.
NO_ROOT does not seem to be documented outside of the source code.

-- 
Andriy Gapon