Support downloading pyproject.toml build deps with parameter

[nanonyme]

What's the problem this feature will solve?

When giving --no-binary :all: currently build dependencies are omitted. So the list of packages for offline install is incomplete.

Describe the solution you'd like

Please provide a parameter that allows downloading complete build dependencies to a directory.

Alternative Solutions

I have not tried alternative tools but would be open to suggested solutions. We essentially need this full list for reproducible offline building of wheels from sources.

Additional context

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[AdamWRichardson]

I too would also be interested in this feature!

[uranusjr]

Pull requests are welcomed. I think it’s reasonable to perhaps do this with pip download --use-feature=include-build-deps as a start.