As a distinct example of a complete build, you can take a look at Earthly's own build. Earthly builds itself, and the build files are available on GitHub:
Earthfile - the root build file
buildkitd/Earthfile - the build of the buildkit daemon
earthfile2llb/parser/Earthfile - the build of the parser, which generates .go files
examples/tests/Earthfile - system and smoke tests
contrib/earthfile-syntax-highlighting/Earthfile - the build of the VS Code extension
To invoke Earthly's build, check out the code and then run the following in the root of the repository
earthly +all