The packages has to be installed by root but they would be installed
insecurely, owned by the uid of the unprivileged user that made the package.
The local user with that uid could thus write to /usr/local/bin/hg .
bdist_mpkg calls out to pax to create the package, but pax do apparently not
have the power to control what it is writing.
Instead, patch the pax files and set their uid fields to 0 before they are
wrapped in a dmg.
