Since c597d591b56a2a9ed355c57a717d1b2ed4c31aa9 the release script uses
acbuild instead of actool, so purge all the references and have the
release script check for acbuild's presence instead.
Release guide steps to artifacts signing defaults to binary
signatures, while producing .asc files.
This commit changes to armored signatures, also matching appc
requirements.
Fixes#5594