Blocker 893751 (porting build_packages to chromite) isn't strictly required if we have a time crunch here, but would be really nice to have done first.

build_packages itself is maybe a 2, but I'm not as familiar with the rest of what it's doing, so (hopefully) padding a bit in case it gets messy. As I get closer to working on this I will need to have a closer look at whether it makes sense to split out the setup into a separate stage.

athilenius@/lannm@: There's also some CI work being done at the end of this stage. For the artifact being uploaded I can just pass back a file path or whatever you prefer. The whole update metadata section of that stage (https://cs.chromium.org/chromium/src/third_party/chromite/cbuildbot/stages/build_stages.py?q=BuildPack&sq=package:chromium&g=0&l=664) is updating a CBuildbotMetadata class. Is that whole section at all relevant?

We'll need a general solution for pushing metadata back out of scripts in any case. Lets focus on making that easy and then we can default to sending more info than we really need.