When populating the dvd/packages/ directory, create
a symlink to All/pkg-*.txz in the Latest/ directory.

This allows 'pkg bootstrap' to work out-of-box if
the REPOS_DIR environment is properly set.

Tested on:	stable/10@r271848
MFC after:	3 days
X-MFC-10.1:	yes
Sponsored by:	The FreeBSD Foundation


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271876 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f