Documented my setting up the TeamCity agents because:

1. TeamCity documentation is shit. Some things are implied and many defaults are either not explained, not provided, or both.
2. TeamCity errors give no information and look like this: Incompatible Runner: Command Line
3. I don't want to have to figure this stuff out again when we migrate away from Debian Stretch.

Diff CI machines are currently running this configuration. Some additional tweaks are required to run IBD and nightly builds, which I will follow up on later.