This will create `build-chunk-$n.json` files for steps that should run
_before_ duck, and `post-chunk-$n.json` files for steps that should
run after duck.
The post steps are not yet uploaded to Buildkite, but we also don't
have any right now.
Change-Id: I7e1b59cf55a8bf1d97266f6e988aa496959077bf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5047
Tested-by: BuildkiteCI
Reviewed-by: ezemtsov <eugene.zemtsov@gmail.com>
Autosubmit: tazjin <tazjin@tvl.su>
5a88e47b71