For macOS, set install_name to @rpath/libNAME.dylib and use it

For the SBBS binaries, set @executable_path and
@executable_path/../${LIBODIR} so they can all be in one dir, or
they can be in the build output dirs and still work.

For utilities, set to @executable_path and
@executable_path/../../${LIBODIR} for the same reason.

With this, we shouldn't need to fiddle with DYLD_LIBRARY_PATH