build: build deb/rpm independently on config/extensions in the host system
Reverts 5aac617a028d and replaces it with a more general solution.
- works for both rpm and deb
- sidesteps eventual problems with local extensions that have nothing to do with
the build process (hg-git, for example, fails with version 4.4 because
dedab036215d removed peerrepository, and hg-git still uses it as of 0.8.9)
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)