New comment by sgn on void-packages repository

https://github.com/void-linux/void-packages/issues/20150#issuecomment-600528830

Comment:
Our project provides `sys/cdefs.h` for musl by `musl-legacy-compat`.

Proper solution is patching it and report to upstream. Meanwhile,
```
makedepend+="musl-legacy-compat"
```