goinstall: undo 1ad616fb313d (always rebuild...)
goinstall: undo 1ad616fb313d (always rebuild...)

CL 4627051 is a better way of doing the same thing.

R=golang-dev, r
CC=golang-dev
http://codereview.appspot.com/4654045

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang