Concept

How the whole new sbuild+multibuild works right now

1. sbuild [params] *.dsc is called

2. sbuild will spawn a multibuild-wrapper (thus runs as buildd user) and talk to it through control pipe

3. multibuild-wrapper will read available hooks and select those from the config (~/.sbuildrc) which are activated

4. multibuild-wrapper will call hooks according to pipe input and available hooks. User-provided hooks need to be in ~/.multibuild/builder/hooks/... (like environment-own)