This is the OG pre-UAHF sighash from Bitcoin, which is invalid on eCash, but still can be used on Bitcoin, Dogecoin and others.
Note: This cannot be tested on eCash as regtest will never run legacy sigchecks. There, IS_LEGACY_MODE must be commited as false.
This is a forwardport of https://github.com/dogecash-io/dogecash/pull/80.