KDE4 build question: turning off hidden visibility?

[René J.V. Bertin]

Hi,

Please excuse me for a question that's not directly related to KF5 frameworks; I don't know where else to reach an audience who might know (remember) the answer.

In short: how do I configure a build so it will use default (public) visibility for all symbols, preferably without patching something installed by kdelibs?

I'm assisting someone getting a KDE4 project to build on the latest Mac OS (10.14 "Mojave") which I cannot currently run myself. The project in question fails with a bunch of missing symbol errors at the link stage which I cannot reproduce on the OS version I am running myself. Not even when we both use the same stock compiler and linker (clang 5/ld64-latest from MacPorts) and, as far as I have seen, identical code-generation and linker options.
https://trac.macports.org/ticket/57332

This really has me stymied...