If you Google "crt_externs.h darwin", you will see that this approach
is very widely used for many packages include wine, 4Suite, ruby, etc.
We can take this over to the darwin developer mailing list but they
will tell you the same thing I am. It is bad form to create shared
libraries with undefined symbols that have to be created as a special
case. Better to handle that in the shared library than to inflict that
onto the developer using it.