configure error on macOS : cannot find zlib

[xpech]

Configure is not able to find zlib.h on macOS.

Adding /opt/local on config.m4 line 43 resolve the issue.

I'm not allowed top send you a branch or PR.

Hope this helps,

[Moskito89]

If you are using Homebrew, you can run ./configure --with-zlib-dir=/opt/homebrew/opt/zlib too.

[NoiseByNorthwest]

Would it be relevant to make config.m4 handle /opt/local as in @xpech 's screenshot ?

[xpech]

There is two package manager under macOS, Homebrew and Macport. For Macport user adding this search path fix the lib search issue. Using --with-zlib-dir not working.
The fix broke nothing else.