Ignore MachO-specific flag -search_paths_first, since it is the default
in zld and ld64.

Also see Jakub's comment[1]:

    Changing topic slightly, @motiejus dunno if you noticed, with this
    change building arm64 Zig binary fails on macos - it complains about
    unknown -search_paths_first flag. This one is an easy fix: we should
    ignore it since this is the default behaviour in both ld64 and zld.

[1]: https://github.com/ziglang/zig/pull/11906#issuecomment-1163545849