Justine says nay for the time being. Only XNU implements this. It's not
clear what ABI XNU is using but it's obviously not the one in the POSIX
documentation link below. Since all platforms implement vfork, it might
be better to empirically gauge the intersection of consensus which will
have better performance than this interface.
https://pubs.opengroup.org/onlinepubs/009696699/xrat/xsh_chap03.html
