Refine #3277
According to what I read on the internet, on OSX, both MH_BUNDLE (module)
and MH_DYLIB (shared library) can be dynamically loaded using dlopen(), but
it is not possible to link against MH_BUNDLE as if they were shared
libraries.
Metion this as an issue in the documentation.
Emitting a warning, and then going on to fail during the build with
mysterious errors in symbolextractor isn't very helpful, so make attempting
this an error on OSX.
Add a test for that.
See also:
https://docstore.mik.ua/orelly/unix3/mac/ch05_03.htmhttps://stackoverflow.com/questions/2339679/what-are-the-differences-between-so-and-dylib-on-osx