cmd/dist: fix memory bug (fix builders?)
cmd/dist: fix memory bug (fix builders?)

Thanks, Valgrind!

TBR=golang-dev
CC=golang-dev
http://codereview.appspot.com/5630050

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