Help! 
A clean install on Linux ubuntu.
/waf configure --board=px4-v2
./waf build --target examples/BARO_generic --upload
All goes fine until:
All done!
ninja: build stopped: subcommand failed.
- Node /home/maciek/REPOS/svn/mackowe/drony/ArduPilot/Ardu/ardupilot/build/px4-v2/modules/PX4Firmware/CMakeCache.txt is created more than once (full message on ‘waf -v -v’)
. The task generators are:
1. ‘px4_msg_gen’ in /home/maciek/REPOS/svn/mackowe/drony/ArduPilot/Ardu/ardupilot
2. ‘examples/BARO_generic’ in /home/maciek/REPOS/svn/mackowe/drony/ArduPilot/Ardu/ardupilot/libraries/AP_Baro/examples/BARO_generic
If you think that this is an error, set no_errcheck_out on the task instance
Waf: Leaving directory `/home/maciek/REPOS/svn/mackowe/drony/ArduPilot/Ardu/ardupilot/build/px4-v2’
EDIT: I can compile ‘make px4-v2’ in the Copter dir, but “./waf copter” also fails with a similar error.
EDIT2: compiles on ubuntu 16.04. Does not compile on ubuntu 18.10.