[CMake] How to use a generated linker map with a shared library?

[Paul Smith]

On Tue, 2017-01-17 at 13:20 -0500, Paul Smith wrote:
> I wonder whether _fini and _init need to be exported in order to
> properly handle global ctor/dtor when the library is loaded/unloaded?
>  Hm.  I may need to do some experimentation here.

FWIW I tried some experimentation with both dynamic linking and
dlopen()/dlclose() methods of loading the shared library, and all my
global ctors and dtors appeared to be invoked as expected in both
situations regardless of whether the _fini and _init symbols were
public...

So I dunno.