[build-command] Use uv to install Python deps for CI

[echoix]

I just wanted to try it out with an upcoming PR, and it’s quite impressive.
With cached dependencies, the old way method took 25-40s to install the deps. (https://github.com/echoix/megalinter/actions/runs/9121261204/job/25080127542#step:8:1 and https://github.com/echoix/megalinter/actions/runs/9120700814/job/25078549631#step:8:1)

Here, WITHOUT cached dependencies, it took less than 5 secs (https://github.com/echoix/megalinter/actions/runs/9121318153/job/25080283053#step:9:1)

I used the pip to install uv, but it could’ve been with the shell script one liner.

I had to use the --system flag to let it use the global install in CI, and to not require a venv.

Otherwise, it’s quite easy.

Proposed Changes

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Readiness Checklist

Author/Contributor

• Add entry to the CHANGELOG listing the change and linking to the corresponding issue (if appropriate)
• If documentation is needed for this change, has that been included in this pull request

Reviewing Maintainer

• Label as breaking if this is a large fundamental change
• Label as either automation, bug, documentation, enhancement, infrastructure, or performance

[nvuillam]

@echoix that's amazing ^^

What about ascending dependency ? For example, what happens to repos using pip install in PRE_COMMANDS ?

If this is a breaking change, we can't merge this PR before the next major release

[echoix]

It is only inside the build command when used by us in a comment to rebuild the generated files on a PR.

But to answer your question, the maintainer of the UV repo answered the other day that a venv populated by uv is undistinguishable from the venv's point of view, and can be further modified by it. So as a docker build step tool, it is ideal. But in this PR, it isn't in any docker script.

[echoix]

Since a required check was skipped, it will need to be force merged @nvuillam

[nvuillam]

@echoix great ')
Merged ^^