I’ve been a Software Engineer on various PowerShell teams since 2013 and at Microsoft since 1999. I was involved in open sourcing PowerShell and moved over the core PowerShell engine shortly after we announced the project.
For PowerShell Core, we basically had to build a new engineering system to build and release it. How we build it has evolved over time as we learn and our other teams have implemented features that make some tasks easier. We are finally at a state that we believe we can engineer a system that builds PowerShell Core for release with as little human interaction as necessary.