You can do this on macOS too, if you're willing to break all forward/backward compatibility and make direct syscalls you can have a purely static binary. Without the LC_LOAD_DYLINKER command on the mach-o binary the kernel should just jump to the entrypoint based on LC_UNIXTHREAD. (This may not longer work on arm machines though if they actually trap on direct syscalls not through libSystem, similar to the BSDs)