Failed to build omnibus-gitlab using `ubuntu_18.04:1.5.0` image

When building the omnibus-gitlab package for Ubuntu 18.04 using builder with version 1.5.0. The following error shows up constantly.

$ bin/omnibus build gitlab
Activating bundler (~> 2.2) failed:
Could not find 'bundler' (2.2.15) required by your /builds/dit/omnibus-gitlab/Gemfile.lock.
To update to the latest version installed on your system, run `bundle update --bundler`.
To install the missing version, run `gem install bundler:2.2.15`
Checked in 'GEM_PATH=/root/.gem/ruby/2.7.0:/usr/local/lib/ruby/gems/2.7.0', execute `gem env` for more information
To install the version of bundler this project requires, run `gem install bundler -v '~> 2.2'`

We should install the bundler version which is the same as what is used in omnibus-gitlab