* build_root - Full path to the work directory that holds the local git checkout and the temp directory where the test runs.
* animal - Set the host alias assigned to you by the BuildFarm administrators.
* secret - The secret assigned to you by the BuildFarm adminstrator. In the words of Gandalf, "keep it secret, keep it safe."
+* optional_steps - Uncomment build_docs and/or make_test in order to include building those stages. Extra packages are required for building documentation, documented elsewhere.
### Enabling exim features
In order to enable exim features, you'll use the `makefile_set`, `makefile_add`, or `makefile_regex` to enable them. Here are some samples: