Makefile: streamline cmake-build and cleanup nuttx_, _default targets
Makefile: streamline cmake-build and
cleanup nuttx_, _default targets

dagar/Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,dagar/Firmware,dagar/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,krbeverx/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,PX4/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware,PX4/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,PX4/Firmware,acfloria/Firmware,krbeverx/Firmware,dagar/Firmware,PX4/Firmware,dagar/Firmware,dagar/Firmware