Add timestamps to package build logs

[Haw Loeung]

Hi,

I think it would be nice to include timestamps of output from package builds. Perhaps pump output through `annotate-output`?

Example:

| https://launchpadlibrarian.net/573488092/buildlog_ubuntu-trusty-amd64.snapd_2.53.4~14.04+git3462.badea55ab~ubuntu14.04.1_BUILDING.txt.gz

This would let us work out which parts of a build seems to be taking a long time. For us Canonical IS SREs, that would help let us compare between the old (lcy01, lgw01) and new builders (lcy02). For package maintainers, it could also help identify areas taking some time when it shouldn't.

All of this could help to reduce package build times.

[Colin Watson (cjwatson)]

I can certainly see how this could be useful, but I'm also concerned that this would add a great deal of noise to build logs. I think it possibly needs to wait until we can present build logs in a more structured kind of way, e.g. by folding sections and having timestamp annotations presented somewhat out of band rather than just all in a big text file.