Allow PushToBuildStorage to only push the asset manifest

[jkoritzinsky]

This allows us to use GenerateBuildManifest to split the "join verticals" job in the VMR and have a "build the merged manifest" job and a "download/upload artifacts" job.

Alternatively, we can remove GenerateBuildManifest (it has no users today) and add a "don't publish artifacts" option to PushToBuildStorage so it just produces the build model.

[ViktorHofer]

This allows us to use GenerateBuildManifest to split the "join verticals" job in the VMR and have a "build the merged manifest" job and a "download/upload artifacts" job.

Do we have an issue that tracks this work? Trying to understand the end goal here.

Alternatively, we can remove GenerateBuildManifest (it has no users today) and add a "don't publish artifacts" option to PushToBuildStorage so it just produces the build model.

This sounds more reasonable to me.

[jkoritzinsky]

This all falls into #15317 as this would allow us to remove our manifest parsing logic in join-verticals.

[jkoritzinsky]

@ViktorHofer I've updated this to instead be an option on PushToBuildStorage and deleted GenerateBuildManifest.

[mmitche]

Let's be sure there is no reference anywhere to GBM, but I like this option better tbh. The next step here, would be that you would supply the artifact names where assets are pushed on the input manifests, and then this task would verify everything is in the right place. This would be the eventual state of all .NET builds.

[jkoritzinsky]

I've already validated that there's definitely no reference. The only reason we have it still is the commit that removed it and the commit that refactored it merged in simultaneously so it was restored right after it was deleted.