What's the problem this feature will solve?

PEP 518 defines a [build-system] section with a required = [] field. But there is no way to tell PEP 517 build front-ends to apply constraints to those build requirements while provisioning an env for them. This makes it hard to go perform predictable builds.

Describe the solution you'd like

I was thinking that pip-tools could facilitate this by either learning to manage that setting in pyproject.toml or by sourcing the requirements from that field to produce a constraints file. The former could allow to keep the builds predictable with any build front-end like pip while the latter would be helpful mostly for more flexible build front-ends like pypa/build that allow the users to provision the envs by themselves.

WDYT folks?

Alternative Solutions

N/A

Additional context

N/A