The package index is generated on first use anyway, therefore it makes no
sense to continue shipping it.

Also sstrip the bundled host binaries when packing the IB to save some
additional space.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@44293 3c298f89-4303-0410-b956-a3cf2f4a3e73