After fighting a bit with the not-entirely-obvious format of NetBSD’s syscalls.master file, and leaning heavily on the existing Darwin and FreeBSD ports, I’m closing on a syscall package that will compile.
The two next steps (that I’m cognizant of!) are:
1. deal with the ELF branding so that NetBSD binaries are generated
2. make it all actually work 
I’ve been a little suprised at just how many system calls are not implemented in the current ports. For a language with aspirations to system programming, I hope that’s just “get 1.0 out the door” haste and not a reluctance to expose all the OS’s functionality.