rm_work: exclude the SSTATETASKS from the rm_work tasks sinature

We can exclude the SSTATETASKS from the rm_work task signature
to avoid running the task when we remove some setscene tasks
from the dependencie chain.

The inject_rm_work handler on the rm_work bbclass triggers the
rm_work task running for any signature change in the dependencie
chain of the task do_build of each recipe.

i.e INHERIT:remove = "create-spdx" will trigger the do_rm_work
when we collect the sstate cache with INHERIT = "create-spdx"

(From OE-Core rev: cc6ade7de20f6fb9dffe43bceb6e513209e2216a)

Signed-off-by: Jose Quaresma <jose.quaresma@foundries.io>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
(cherry picked from commit 77729bea5b17d65dafb604fd1665c612091b28c7)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/rm_work.bbclass

@@ -112,6 +112,8 @@ do_rm_work () {
         fi
     done
 }
+do_rm_work[vardepsexclude] += "SSTATETASKS"
+
 do_rm_work_all () {
     :
 }