macOS has two kinds of loadable libraries: MH_BUNDLE, and MH_DYLIB.
bundle is used for plugins that are loaded with dlopen/dlsym/dlclose.
And there's no way to preload a bundle into an application. dynamic
linker (dyld) will reject it when finds it in DYLD_INSERT_LIBRARIES.

Unfortunately, a bundle is built if -module flag is provided to libtool.
The flag has been removed to build dylibs with ".dylib" suffix.
Signed-off-by: NRoman Bolshakov <r.bolshakov@yadro.com>