uv-build: add a config setting to control compression level

[mgorny]

Summary

While the primary use case for PEP517 build backends is publishing packages for publishing, downstream maintainers are also forced to use them as part of distribution package build process. In this workflow, the built wheels are almost immediately unpacked/installed and discarded. Therefore, compression is not really necessary — usually it is just a waste of energy to compress something only to have to decompress it back.

In Gentoo, we usually work around the problem by patching the zipfile module to disable compression. However, that obviously works only for pure Python backends. Would you consider adding a config_settings option to override the compression level, so that we could disable compression on built wheels in order to save energy?

Example

I imagine we'd use it like:

gpep517 build-wheel --output-fd 3 --wheel-dir dist --config-json '{ "compression_level": 0 }'

[konstin]

Has compressing/decompressing are noticeable performance impact for you, what relative and absolute performance difference do you see?

[mgorny]

I don't know because I haven't seen any package use uv-build yet :-). I'm a perfectionist, though. I suppose I could try checking other Python backends (I suppose zlib would give close enough results) with some big Python packages like Django or ansible, but I'd have to find time when my CPUs aren't all busy.

[konstin]

In this case I'd say we wait until we see adoption and get some real world numbers, if we see a noticeable overhead, we can add the option.