Matthew Pickering authored Mar 07, 2022 and Marge Bot committed Mar 24, 2022

This commit introduces a new script (.gitlab/gen_ci.hs) which generates
a yaml file (.gitlab/jobs.yaml) which contains explicit descriptions for
all the jobs we want to run. The jobs are separated into three
categories:

* validate - jobs run on every MR
* nightly  - jobs run once per day on the master branch
* release  - jobs for producing release artifacts

The generation script is a Haskell program which includes a DSL for
specifying the different jobs. The hope is that it's easier to reason
about the different jobs and how the variables are merged together
rather than the unclear and opaque yaml syntax. The goal is to fix
issues like #21190 once and for all..

The `.gitlab/jobs.yaml` can be generated by running the `.gitlab/generate_jobs`
script. You have to do this manually.

Another consequence of this patch is that we use hadrian for all the
validate, nightly and release builds on all platforms.