New issue by leahneukirchen on void-packages repository

https://github.com/void-linux/void-packages/issues/41769

Description:
### Is this a new report?

Yes

### System Info

n/a

### Package(s) Affected

musl-legacy-compat

### Does a report exist for this bug with the project's home (upstream) and/or another distro?

_No response_

### Expected behaviour

The header implements SPLAY trees.

### Actual behaviour

The header expands into `__unused` tokens which are undefined.

Merely defining `__unused=` is not a workaround as this identifier is used in musl internal headers.

The `__unused` should simply be removed.

### Steps to reproduce

Build stress-ng with musl-legacy-compat enabled.