See #1

Fixes #2

Base image already gives us `build-essential`, but nothing provided
`fakeroot`. :(

```
This package has a Debian revision number but there does not seem to be
an appropriate original tar file or .orig directory in the parent directory;
(expected one of nginx_1.17.0-1~eth.orig.tar.gz, nginx_1.17.0-1~eth.orig.tar.bz2,
nginx_1.17.0-1~eth.orig.tar.lzma,  nginx_1.17.0-1~eth.orig.tar.xz or nginx-package-build.orig)
```

* https://blog.packagecloud.io/debian/debuild/packaging/2015/06/08/buildling-deb-packages-with-debuild/
* https://git.ethitter.com/debian/nginx-build