The build is now fast enough that we can build both faster than we used
to build each individual type.
For context, the fully cached (with `ccache`) build for both takes a
total of about 7 minutes, whereas a non-cached full build of just the
DEBs used to take about 12 minutes. I expect that on average, building
them both when there are source changes (i.e. when only part of the
build is cached) would likely take a total of about 10 minutes.
This machine is not always available, but when it is,
it's much faster (about 5-10 mins) than both the
GitHub Actions CI (3+ hours) and the old private CI machine (1+ hour).
Since darlingserver doesn't need a kernel module, we no longer need a
DKMS package.
Note: I have not tested whether building the `.deb` actually works after
this change. I guess the CI will let me know ¯\_(ツ)_/¯
