Feature request: system package rollback

[MingcongBai]

As per discussion in the group chat, we think an implementation of system package rollback for autobuild is possible. In a process like the following:

1. Autobuild fetches all packages and deps needed for a build.
2. Package being built.
3. After the package is installed (as a test, or not installed depending on configuration), the package itself and all packages introduced by the build will be wiped from the system - forming a rollback.

However, as @Icenowy suggested, this is a unnecessary feature if container exists.