The commits landing in bug 1412932 mucked with some targets in client.mk in such a way that configure can run multiple times during a build. I think it has something to do with the mozconfig.json file. The subsequent configure invocations run during the AUTOMATION tiers. I think this regression is harmless aside from adding a little overhead. It should get fixed as part of porting client.mk's logic out of client.mk. But I'm filing this bug so we have something to track it.