Added information in about the various varflags the user can
use to define the type of archive.
(From yocto-docs rev: 9035c415d4453750f016fe4ea2fa8179549330ca)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>