Here's a patch to locate the base package inside the application bundle on OS-X. The patch also disables the CPSForeground hack in boostrap.cxx, which is unnecessary if the we're running as a proper bundle rather than a Unix command line program.
Both of these changes are only compiled if OSX_BUNDLE is defined (I'm doing this via a setting in ProjectBuilder), so if you're building on OS-X using configure + make, you shouldn't see any chance.