- Add missing dependencies and enable testsuite

- Force onnx static build in cmake round to ensure we do not
end up with unresolvable pkg

- Remove testing fluff from previous change and properly loop
the cmake call for each python variant
- Enable python2 (well rather not explicitly disable it as there
is no need for that at the momment)

- Force building with system cmake to respect system definitions
and to provide debug information for later on