setuptools.package-data has no effect within a docker container

So, I have this little pyproject.toml-based project (named RecordEcos) to do multi-camera recording with a minimalist interface (using PySimpleGUI). The interface make use of a placeholder image when the camera are not connected.

I've added the following section to my pyproject.toml to ensure the image is well embedded into the wheel.

[tool.setuptools.package-data]
RecordEcos = ["*.png"]

And indeed, everything works perfectly on my laptop:

$ python -m build | grep Placeholder
copying RecordEcos/gui/img/Placeholder.png -> RecordEcos-0.4.5/RecordEcos/gui/img
copying RecordEcos/gui/img/Placeholder.png -> build/lib/RecordEcos/gui/img
copying build/lib/RecordEcos/gui/img/Placeholder.png -> build/bdist.linux-x86_64/wheel/RecordEcos/gui/img
adding 'RecordEcos/gui/img/Placeholder.png'

Actually, it's working on my laptop even if I don't add the setuptools package-data option. Which seems to be quite consonant with setuptools documentation.

So I've pushed it to gitlab, the CI has been triggered... And the resulting wheel does not contains the image.
So to be sure, I've try it within a docker image:

laptop $ docker run -it python:3.11 /bin/bash
python-container $ pip install build
python-container $ git clone <repository>
python-container $ cd <repository>
python-container & python -m build | grep Placeholder

The image is not copied !

Does someone have any clue what's happening there ?

I've tried it with the alpine, slim and bookworm variants of python:3.11

Misc informations

laptop under ArchLinux

Python & packages
Python: 3.11.8
build: 1.1.1
setuptools: 65.6.0

gitlab-ci.yml

build:
  stage: build
  image: python:3.11-alpine
  script:
    - pip install build
    - python -m build
  artifacts:
    untracked: false
    when: on_success
    expire_in: "30 days"
    paths:
      - dist/

I don't know this for a fact, but I believe you either need to explicitly call out the package_data argument, or you need to setup a Manifest file.

https://setuptools.pypa.io/en/latest/userguide/miscellaneous.html#using-manifest-in