static GitSmartSubtransport()
 {
     GCHandleOffset = MarshalPortable.OffsetOf <GitSmartSubtransport>(nameof(GCHandle)).ToInt32();
 }
 static GitOdbBackendStream()
 {
     GCHandleOffset = MarshalPortable.OffsetOf <GitOdbBackendStream>(nameof(GCHandle)).ToInt32();
 }