bitbake: cookerdata: Fix tinfoil by adding missinge extra_caches default

(Bitbake rev: d513153cac283aa4ec37135a9190f7a091b6c44b)

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

bitbake/lib/bb/cookerdata.py

@@ -125,6 +125,7 @@ class CookerConfiguration(object):
         self.dump_signatures = False
         self.dry_run = False
         self.tracking = False
+        self.extra_caches = []
 
         self.env = {}