libc detection is not supported

[privatenumber]

Describe the bug

As mentioned in #1161, all package managers support the libc property now. However, libc doesn't seem mocked/supported in WebContaiers.

I tested the detection logic of npm, pnpm, and yarn here, and all of them return null:
https://stackblitz.com/edit/stackblitz-starters-hkv5ph?file=index.js

This causes all libc distributions to get installed.

For example, when installing @swc/core via pnpm, both @swc/core-linux-x64-musl and @swc/core-linux-x64-gnu are installed:

https://stackblitz.com/edit/stackblitz-starters-2ap9g3?file=package.json

Link to the blitz that caused the error

https://stackblitz.com/edit/stackblitz-starters-hkv5ph?file=index.js

Steps to reproduce

Open links above.

Expected behavior

For libc to be mocked, and for the package managers to pick the appropriate libc distribution so extra packages aren't installed unnecessarily.

Parity with Local

• I have run the project in my local machine and I could not reproduce the issue.

Screenshots

No response

Platform

• OS: [e.g. macOS, Windows, Linux]
• Browser: [e.g. Chrome, Safari, Firefox]
• Version: [e.g. 91.1]

Additional context

privatenumber/pkg-size.dev#21 (comment)