considering that you are already in the ardupilot directory, do
ls /build/erlebrain2/* and you should see the files
copy the quadcopter file in a proper place and launch the file manually:
sudo ./arducopter -C udp:10.0.0.1:14550
Note:
you may need to stop the old ardupcopter before
sudo top and hit ‘k’ to kill the ardupilot process (should be the defaulted number) , press enter and type 9 to kill it
Result:
Raspberry Pi 2/3 with BCM2709!
Found PX4Flow on bus 1
Found LidarLite device=0x6209 v2=1
The sensor are recognized 
and then after few seconds
: Segmentation fault … 
Segmentation fault on RPI is a known problem that should have been corrected on copter 3.5 release 7 (the lates from last week). Copter-3.5.0-rc7 is now available for beta testing
Make sure that you have compiled with the latest Master
Or check if you have t->thread->set_stack_size(1024 * 1024); on line 109 in this file: /ardupilot/libraries/AP_HAL_Linux/Scheduler.cpp