Use GetBuildTime from libchrome instead of __DATE__

So that this daemon doesn't change on every build, use the system build
date from libchrome (which reads ro.build.date). That way we don't have
to update this daemon for every OTA.

Bug: 24204119
Change-Id: I136d53e5e4ebb9430a57dace66198d8d704d7ca3