I've been testing this with a similar setup to yours, but maybe we have different options for the SQLite library we're testing against. The default SQLite install on my Mac didn't have loadable extension support compiled in, so I tested with a separate SQLite amalgamation. Its the same version of SQLite that you were testing with.
I'm presuming that you took the default options to 'configure' when you built your SQLite, but if not let me know.