User-space system call stubs are not automatically created.
You have (at least) two options:
1) use syscall(syscall-number, arg0, arg1, ...) to invoke the call..
This is probably easiest
2) add the system call codes to <sys/syscall.h> and to the list in
/usr/src/lib/libc/sys/Makefile.inc and rebuild libc.
- Bill