zeromq/libzmq ? reverse-engineered prompt

Build me the ZeroMQ core messaging library from this repo so it compiles cleanly and I can use it as a drop in messaging engine.

I want the project to build on the default setup in the repo, run the tests, and make sure the main socket based messaging features work, including async message queues, publish subscribe, push pull, and support for the transport protocols mentioned in the docs. If anything is missing or broken, fix it in the code instead of just explaining it.

Please keep the existing public API and make the build work with the project’s current CMake or autotools setup. If you need to check current build or platform details online, do that. Afterward, give me a short summary of what you changed and how to build and test it locally.