classes/sstate: regenerate sstate when signing enabled
This change ensures that the task signatures changes, and therefore
sstate tasks are rerun, when signing is enabled. This has the
positive outcome that if signing is enabled new signed shared state
objects will be produced, rather than just signing shared state
objects for tasks where no work has been performed yet.
The downside of this change is that enabling/disabling sstate object
signing alters the taskhash and results in rebuilding the world.
Signed-off-by: Joshua Lock <jlock@vmware.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
