PACKAGES=ffmpeg not working again like in issue #153
I'm using oznu/homebridge:1.7.9 on an intel NUC.

I'm seeing the same error as in issue #153 

```
/homebridge # ffmpeg
Error relocating /usr/lib/libgnutls.so.30: getrandom: symbol not found
/homebridge #
```

Am I missing something?  Thanks!