A build artifact was accidentally committed to ipaddrcheck (https://github.com/vyos/ipaddrcheck/blob/current/src/ipaddrcheck_functions.o) — due to my double negligence: I didn't add a proper .gitignore to it from the start and didn't notice a .o file in git status before committing.

That was the cause of floating CI failures after the fix for T6744: the fix does work, but when a compiled object file is present, recursive make may assume that it doesn't need to be built, so an outdated code ends up in the binary, instead of the fixed code in ipaddrcheck_functions.c