bitbake: runqueue: Only call into the migrations function if migrations active

This doesn't save much time but does make the profile counts for the
function more accurate which is in itself useful.

(Bitbake rev: d446fa89d206fbc6d098215163c968ea5a8cf4a9)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/runqueue.py

@@ -1959,7 +1959,8 @@ class RunQueueExecute:
         """
 
         self.rq.read_workers()
-        self.process_possible_migrations()
+        if self.updated_taskhash_queue or self.pending_migrations:
+            self.process_possible_migrations()
 
         if not hasattr(self, "sorted_setscene_tids"):
             # Don't want to sort this set every execution