Error with `libwmflite-0.2.so.7` on `heroku-18`

I double checked all the steps (buildpacks in right order, Aptfile up to date) and this is not working for us at the moment.

When logging in `heroku bash` and executing `gm`, I get:

```
gm: error while loading shared libraries: libwmflite-0.2.so.7: cannot open shared object file: No such file or directory
```

I could not find any reference to that problem.
 