As leisti noted, the problem with the example is that \bwins\bluetoothlibraryu.def and \eabi\bluetoothlibraryu.def are located in the wrong directory - they should be under \BluetoothLibrary. If the build tools do not find the .def file, nothing is exported from the library and import libraries are not generated. This is what the "not frozen" error means.
Sometimes you'll see the .def files missing altogether from a project, especially if you're porting a Qt library to Symbian platform. In that case, you can freeze the project and generate .def files with:
After the .def file has been generated, you'll have to call 'make release-<target>' once more to build the import libraries.
abld freeze [winscw|gcce]