I have had the same problem. The @linker_flags array in the file inc/GSBuilder.pm contained '-shared' as first element. -shared is not compatible w/ -bundle which was also one of the elements in the array. I solved the issue by modifying the file inc/GSBuilder.pm (it's read only so you'll have to chmod +w inc/GSBuilder.pm first), and add the following command on line 124 of inc/GSBuilder.pm as found in Math::GSL version 0.25:

shift @linker_flags;

This removes the first element of the array i.e. the '-shared' and compilation and tests passed flawlessly. If -shared is not the first element splice it out!

This is probably a dirty fix. Ideally I'd like to understand how the -shared got their in the first place. But that's for another time. Hope this helps. Cheers.