Add release tarball comparison script
The util/release-tarball-comparison.sh
script compares a release-ready
BIND 9 tarball to a temporary BIND 9 tarball created from the same
signed Git tag to ensure that their content does not differ
(significantly).
Supersedes isc-projects/images!211
Documentation: https://gitlab.isc.org/isc-private/bind9/-/wikis/Detecting-build-infra-compromise-during-release-process