Hello, OpenBSD 7.9 and -CURRENT have timer_* stubs functions only ever returning ENOSYS. See: lib/libc/sys/timer_*.c
Thankfully they are undeclared in the public headers, but clang(1) doesn't defaults to -Werror=implicit-function-declaration and having stubs means the linking step doesn't fails. So broken compilation just continues on, and detecting lack of support of the standard timer_* functions becomes a bit harder than it could be. Best regards
