[9fans] undefined reference to `sched_yield'

[Matt]

OpenBSD 4.0 running in QEmu 0.8.2 on FreeBSD 6.0

# cd /usr/local/plan9
# ./INSTALL
* Resetting /usr/local/plan9/config
* Building everything (be patient)...
>>> cd /usr/local/plan9/src/cmd; mk all                   
9l -o o.9p 9p.o
/usr/local/plan9/src/lib9/sleep.c:25: undefined reference to `sched_yield'
collect2: ld returned 1 exit status
mk: 9l -o o.9p ...  : exit status=exit(1)
mk: for i in ...  : exit status=exit(1)
#

MD5 (plan9port.tgz) = e6aba1ebf35fe0407304069dd1ea35c8