Macro rustix::weak::weak_or_syscall

macro_rules! weak_or_syscall {
    ($vis:vis fn $name:ident($($arg_name:ident: $t:ty),*) via $sys_name:ident -> $ret:ty) => { ... };
}

A combination of weakcall and syscall. Use the libc function if it’s available, and fall back to libc::syscall otherwise.