net/libzmq4: Fix build with libc++ 16

Like recent versions of GNU libstdc++, libc++ 16 now has a static
assertion to ensure that custom allocators have the correct rebind
member, and this assertion fires error when building.

Upstream fixed this in
https://github.com/zeromq/libzmq/commit/438d5d88, so apply that patch.

PR: 271850