dashboard/env: fix 32-bit builds
dashboard/env: fix 32-bit builds

(Fix from adg)

LGTM=adg
R=adg
CC=golang-codereviews
https://golang.org/cl/136760043

golang/build,proppy/build,golang/build,golang/build,golang/build,proppy/build,evandbrown/build,evandbrown/build,evandbrown/build,proppy/build,proppy/build