unitypackage_util returns empty dump for any package on MacOS (silicon, M1)

```sh
% ./unitypackage_util ../pf.unitypackage dump
{}
```

```sh
% ./unitypackage_util ../pf.unitypackage info
Package: TarGz: ../pf.unitypackage
```

```sh
% ./unitypackage_util -V
unitypackage_util 0.1.3
```
