As of yesterday, the build-system git should also be capable of building Tvheadend. I have introduced a diff-scheme similar to the one in use for OpenPLi.
The patches in the diffs provided in the git also permit #if defined(BOX_NAME) / #endif constructions in code with BOX_NAME the name internally used in the buildsytem, like fortis_hdbox, atevio7500, and so on, but written in uppercase.
Unfortunately I do not know how to use the CI-slots in Tvheadend, However, the necessary drivers are built and loaded in the rcS-routines provided.
Regards,
Audioniek.