I like the idea of testing build-system behaviors like this, and I don’t think it’s ever really done in practice. Scriptable build systems, for lack of a better name for them, exist at a bad intersection of Turing complete, hard to test different cases, hard to reason about, hard to read the build script code, and most of us treating them as “ugh I hope all this stuff works” and if it does “thank god I get to ignore all this stuff for another 6 months”.
If you mean testing the "disable Landlock if the headers and syscalls are out of sync" functionality then I agree, workarounds for such corner cases are often not fully tested.
But it would have been enough here to have a test just to see that Landlock works in general. That test would have broken with this commit, because that's what the commit actually does - break all Landlock support.
Based on that it sounds like there wasn't a test for Landlock integration, if I've understood things correctly.
