Add verbosity handling and pass through to pypa/build

[agriyakhetarpal]

I finally decided to take up #222. This PR exposes verbosity via -v and -vv CLI flags (stackable). They are passed along to pypa/build's _ctx.VERBOSITY. It controls pypa/build's own subprocess calls for uv/pip installs. Build backend commands (meson, cmake, gcc wrappers, etc.) are always visible regardless of verbosity.

Closes #222

TODO:

• Update docs
• Add some basic tests

[agriyakhetarpal]

I have set up the plumbing here but pyodide build -v and pyodide build -vv both return the same output to me, as the default no-verbose-flag build, so this needs an investigation. Maybe the logger is not set up correctly.

[agriyakhetarpal]

The logger is indeed not set up correctly, as pypa/build uses print calls and it prints to sys.stderr, but we print to sys.stdout, so something about our Rich logger swallows it and prevents it from reaching the fd, and I don't know what.

[ryanking13]

Thanks for handling this. I left some comments but overall it looks good to me

[ryanking13]

Maybe this can be moved to vendor/_pypabuild as well.

[agriyakhetarpal]

Hmm, I'd like to keep this one here itself, as it's something that we are implementing (even though we keep it private). It is not vendored from pypa/build.

[ryanking13]

Sure, that's fine.

[ryanking13]

Thanks!

[agriyakhetarpal]

Thanks for reviewing!