Blender and probably other applications: libicu* tends to break because it is versioned

Workaround:

```
FreeBSD% cd "/home/user/Applications/Blender 2.91.0.app/Resources/usr/local/lib/"
FreeBSD% ln -s /usr/local/lib/libicudata.so libicudata.so.69
FreeBSD% ln -s /usr/local/lib/libicuuc.so libicuuc.so.69
FreeBSD% ln -s /usr/local/lib/libicui18n.so libicui18n.so.69
```

Maybe we should do something like this for all our AppImages. Because the version of libicu* will get updated on the target systems, at which point the AppDir still needs to be able to find it...