[release] v5.0.3 stable version

- fix Paparazzi Center on Mac OS (detection of child processes exitting)
  [#290] (https://github.com/paparazzi/paparazzi/issues/290)
- state interface: fix stateCalcHorizontalSpeedNorm_i
- fix/improve dependency generation for building firmware
- abort with meaningful error if ARM toolchain is not found