misc/dist: don't lose mode bits when setting tar permissions
misc/dist: don't lose mode bits when setting tar permissions

R=golang-dev, bsiegert, rsc
CC=golang-dev
http://codereview.appspot.com/5822046

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