[PhilipDeegan]

On macOS, a shared (non embed) build gets -undefined dynamic_lookup, so an extension module resolves the Python C API from the interpreter that loads it rather than linking libpython, the usual way to build extension modules there.

#if defined(__APPLE__)
  if (!embed && a.state().buildMode != mkn::mod::Mode::STAT)
    a.compilerState().add(mkn::mod::LinkPrefixInput{"-undefined dynamic_lookup"});
#endif

No change on other platforms. Built with -W 9 on Linux; macOS CI is the check.