systemd is indeed the bane of Linux, and a pain in the ass for a lot of FOSS. Once the main distributions made it mandatory to install (not just the default, but mandatory) - we've started to see this sort of bifrucation of a lot more FOSS away from being standard-based and multi-platform to being Linux-specific.

That said - I think a rule-of-thumb one can follow is that any inclusion of a file with a directory prefix, especially `<sys/whatever>`, needs a guarantee-of-availability in your build configuration phase, e.g. CMake `find_package()`, or or at least `check_include_file()` and such. That way, you might be more likely to fail to build, but at least you'll be telling the user "I expect these things to be present".