WAY MORE UP-TO-DATE GIST (and includes some setup stuff that I forgot to document): https://gist.github.com/sarimarton/471e9ff8046cc746f6ecb8340f942647
Current Development for Building Libre-version of CrossOver: https://github.com/GabLeRoux/macos-crossover-cloud-build.
For Latest Discussions: https://github.com/GabLeRoux/macos-crossover-cloud-build/issues.
This version of gist is outdated since it was written while I was compiling CrossOver v19. and seems to be there are some breaking changes in v19.1+ and 20. Also, I think I missed some required libraries/stub files that was required in build (that I previously installed beforehand). Oops.