This will make it easier to upload logs to the right place, especially in the cases where a test fails before being able to download/unpack/inspect a build to see what its buildid is.

We do this already in mobile test side, but could easily do it build side after a build. The relevant code is: http://hg.mozilla.org/build/buildbotcustom/file/250110f56a64/process/mobiletestfactoryrw.py#l154 through line 162 and the associated parse_build_info We don't need to use the lambda to do this on desktop, but if we do it will make merging mobile back in easier!

we've been doing this for a while