build: build correct cmd/dist matching GOHOSTARCH         Fix for issue 3210 comment #1.
build: build correct cmd/dist matching GOHOSTARCH
        Fix for issue 3210 comment #1.

R=adg, rsc
CC=golang-dev
http://codereview.appspot.com/5794057

dsriram/golang,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,dsriram/golang,gnanderson/go,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,gnanderson/go,dsriram/golang,tv42/old-go,dsriram/golang,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,gnanderson/go,pombredanne/go-deleteme,tv42/old-go,dsriram/golang,pombredanne/go-deleteme,tv42/old-go,apparentlymart/golang,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,dsriram/golang,apparentlymart/golang,apparentlymart/golang,pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang,gnanderson/go,gnanderson/go