Please add building of manifests in build job for HAC base images.

Description from the Milestone doc:

[Carry-Over from M8] HAC: Onboard repos with HACBS builds, or note here that the security checks are taken care of elsewhere. We’re trying to meet the requirement for manifest generation: SSML-8108 as well as verifying that your images are signed. Ref: HAC ESS Assessment. Feature: https://issues.redhat.com/browse/STONE-203