I had also to work on the configuration of the shrinkwrap/shrinkpack tooling. The former configuration and especially the shrinkwrap.json.in file blocked the build process of the docker file. The naming of the shrinkpacked files changed.
Once this was fixed the browser part of LibreOffice was build sucessfully. And finally I was able to build a first lool docker container and start it.
I made a first test and could copy the loolwsd.xml from the container and also view the container log.