This reduces the image size from around 2.2GB down to 100MB. This is to,
hopefully, reduce issues we're seeing where our pipelines are running
out of disk space.
We choose a SHA here as this repo does not contain any useable tags and
it does not seem that they keep tagged versions. Tracking master would
probably be too risky as backwards incompatible changes could come up
and break our CI environment which would be quite time consuming to
debug.
Per
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/108937#note_1257390002
This renames `zoekt-ci-image` so that we can have a versioned
`zoekt-ci-image-1.0`. This will allow us to make changes and bump the
version if we end up with breaking changes.
This still targets a fork of Zoekt because we're waiting on
[1 more PR](https://github.com/sourcegraph/zoekt/pull/496)
to be merged before we can target the main repository. At this point
we'll change the cloning command and check out a stable SHA or tag from
the main repo rather than tracking a branch like this is doing now.
