Who doesn’t know something like this:

FROM alpine:latest

RUN apk add make

Just to then be able to specify somewhere in your CI

make

make is just an example, but I often see containers with only one or two packages added.

These kinds of containers are usually used for a simple build step.
There are 2 typical approaches which both have their downside:

• I use a Containerfile as above to generate an image
  This means I need to build a container & upload it to a registry first.
  Building docker images in a CI is not always trivial (though it’s gotten better) and requires a bit of extra effort like an extra build/upload step in the CI, a registry I can upload it to, secrets to authenticate against the registry...
• I run the command directly in the CI.
  It has to run every time the CI runs - which means a lot of unnecessary compute & wait time!
  But given that the previous solution requires a bit of time to set up, this is the “lets’ get it done quickly” approach often taken

Now let me introduce to you another way to solve this small annoyance.

Nixery

Nixery is a “container registry” which can produce a minimal container image with only the packages you need. For example when I pull the image nixery.dev/bash/gnumake/musl it will generate an image with the 3 specified packages bash, gnumake and musl ad-hoc. The packages are built from Nixpkgs and copied into the container including their own dependencies. This is done on the server at “pulltime”. That means all I do is specify the above container to pull and I don’t need any extra step.

So an example gitlab-ci task which I actually used to run an install step which just copies files into the install directory to be packaged in a later phase:

build:
  stage: install
  image: nixery.dev/bash/gnumake/musl
  script:
    - make install
  artifacts:
    untracked: false
    paths:
      - install

...

stages:
  - install
  - package

What packages can I use that way? MANY! According to repology it’s the repository with by far the most packages. There’s also a search where you can check if a package you require in your container is available (and how it’s called).
And if you’re a bit of a nerd; it’s not even that hard to add a new package to the nixpkgs repository. At least much easier than getting a package into any of the major distributions.