make check errors on recent MacOS versions appear to be due to new default linker in XCode

[Hans Åberg]

> On 3 Oct 2024, at 19:20, Mark Mentovai <mark at mentovai.com> wrote:
> 
> Hans Åberg wrote:
> Of what importance is -flat_namespace to GMP? —Specifically, does it help performance?
> 
> It’s not important to gmp.
> …

Thank you for this informative description.