Upgrade Omnibus Builder to v1.6.0
This brings in the Go v1.16.4 update (gitlab-omnibus-builder!177 (merged)) among other changes: gitlab-omnibus-builder@1.2.0...1.6.0
Edited by Stan Hu
This brings in the Go v1.16.4 update (gitlab-omnibus-builder!177 (merged)) among other changes: gitlab-omnibus-builder@1.2.0...1.6.0