The keyring to build with. By default, we will attempt to figure out if we are building a Debian package on Ubuntu, and if we think that we are this will be set to /usr/share/keyrings/debian-archive-keyring.gpg. This file is part of the debian-archive-keyring package. If you need to use a custom keyring, put it in here. If for some reason the auto-detection is not working properly, set this to the string 'disabled' and no keyring settings for pbuilder will be set.