Unify build system

honestly not super happy with this, but it's a start.

I guess the next steps are to clean this up a little, then get everything building with newer lvgl and drop lv_drivers.

Then, finally, we can get unl0kr working with the LVGL simulator so it can be tested properly, and we can start working on new apps.

The code changes are include fixes, and reworking squeek2lvgl to be a proper library rather than randomly relying on two variable specified in unl0kr code. This way it can be build standalone and linked in nicely.