package/pkg-generic: add host-tar dependency for downloads from repositories

package/pkg-generic: add host-tar dependency for downloads from repositories

Three of our download backends need a host tar that can generate
reproducible archives: cvs, git, and svn. The other two, bzr and hg,
use their internal implementation.

So, for those three that need it, and a dependency on host-tar when the
system tar is not appropriate.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>