| ## Add a system type dependency for zlib | |
| This allows zlib to be detected on macOS and FreeBSD without the use of | |
| pkg-config or cmake, neither of which are part of the base install on those | |
| OSes (but zlib is). | |
| A side effect of this change is that `dependency('zlib')` also works with | |
| cmake instead of requiring `dependency('ZLIB')`. |