cmd/dist: pass -m32 or -m64 to link too, not just compile
cmd/dist: pass -m32 or -m64 to link too, not just compile

R=golang-dev, iant
CC=golang-dev
http://codereview.appspot.com/5646053

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go