cmd/makemac: add govc env vars to systemd service file
cmd/makemac: add govc env vars to systemd service file

Fixes golang/go#20224

Change-Id: Iae7d70bdf0950541d774d12077552153ce1a15e0
Reviewed-on: https://go-review.googlesource.com/46332
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,golang/build,golang/build,golang/build