qml2cpp output should be deterministic

The emitted cpp should not change if nothing has changed in qml. Currently rebuilding the same application several times, will output different cpp.

For example, between two clean builds data generated in qul_font_engines.cpp can be different. To be more detailed - it seems like data is always same, but can be generated in different order.

It seems like issue is easier to reproduce, when application uses several different fonts (3-4)