There's a merged pull request on the void-packages repository

mhash: make boolean usage musl C++ portable.
https://github.com/void-linux/void-packages/pull/46005

Description:
#### Testing the changes
- I tested the changes in this PR: **YES**

#### Local build testing
- I built this PR locally for my native architecture, (`x86_64-glibc`)
- I built this PR locally for these architectures:
  - `x86_64-musl` (crossbuild)
  - `i686` (crossbuild)

mhash uses `_Bool` directly for `#define mhash_boolean _Bool`. [musl C++ doesn't define `_Bool`](https://www.openwall.com/lists/musl/2017/07/28/1), so any C++ projects that include it will fail to build on musl. This fixes that without impacting any C projects