misc/dashboard/builder: reinstate 'go get -d' error handling hack
misc/dashboard/builder: reinstate 'go get -d' error handling hack

I thought this was redundant since the behavior of 'go get -d' had
changed. I was wrong. Should have tested more thoroughly.

R=golang-dev, minux.ma
CC=golang-dev
http://codereview.appspot.com/6500136

wesolows/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old