.arcconfig

packaging: "make deb" no longer fails

Release 4.7 rationalized the layout of the build scripts.
Unfortunately, while "make docker-ubuntu-*" and "make docker-debian-*" worked as
expected, "make deb" was broken.

Before this change "make deb" was failing with the following error:
    You are not inside a Mercurial repository!

Or, after the latest changes:
    You are inside <fullpath>, which is not the root of a Mercurial repository

Moreover, when "make deb" failed, the cleanup routine deleted the wrong
directory (contrib/packaging/debian instead of <reporoot>/debian) resulting in
a corrupted working copy that needed to be hg revert-ed.

After this change the docker targets continue to work, and the deb one is able
to finish.

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}