builder: update for os.Wait changes.
builder: update for os.Wait changes.

This compiles again.

R=golang-dev, minux.ma, rsc
CC=golang-dev
http://codereview.appspot.com/5687078

gnanderson/go,tv42/old-go,gnanderson/go,dsriram/golang,tv42/old-go,dsriram/golang,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,dsriram/golang,dsriram/golang,pombredanne/go-deleteme,tv42/old-go,dsriram/golang,apparentlymart/golang,tv42/old-go,gnanderson/go,pombredanne/go-deleteme,gnanderson/go,tv42/old-go,gnanderson/go,apparentlymart/golang,apparentlymart/golang,gnanderson/go,tv42/old-go,apparentlymart/golang,apparentlymart/golang,dsriram/golang,pombredanne/go-deleteme,dsriram/golang