bitcoin#18145: add Wreturn-type to Werror flags
bitcoin#18145: add Wreturn-type to Werror flags

UdjinM6/dash,thelazier/dash,UdjinM6/dash,dashpay/dash,thelazier/dash,dashpay/dash,UdjinM6/dash,UdjinM6/dash,dashpay/dash,thelazier/dash,UdjinM6/dash,thelazier/dash,dashpay/dash,thelazier/dash,dashpay/dash