tools/v23: start populating some buildinfo through the v23 tool
tools/v23: start populating some buildinfo through the v23 tool

For now, add user, timestamp, and platform.

Change-Id: I1a495895d6b11f0486dd131463611252680e2d75

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools