bitbake: runqueue.py: Wipe out the stamp cache between setscene and main task execution

The stamp files can change during setscene and the cache should be cleared to
account for this.

(Bitbake rev: 5ec12f586a50fce675b268965b3dc487aaa96c43)

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

bitbake/lib/bb/runqueue.py

@@ -1170,6 +1170,8 @@ class RunQueueExecuteTasks(RunQueueExecute):
 
         self.stats = RunQueueStats(len(self.rqdata.runq_fnid))
 
+        self.stampcache = {}
+
         # Mark initial buildable tasks
         for task in xrange(self.stats.total):
             self.runq_running.append(0)