Hello! I found solution for me. I use Ubuntu 16.04 and upload firmware to Pixhawk 2.1
I make same 1-4 steps, but 5 is different.
BUILD section
Build directory: /home/stepan/src/Firmware-build
RUN section
Make custom executable.
Executable: make
Command line arguments: px4_fmu-3v_default upload
Working directory: /home/stepan/src/Firmware
Then click run.