Because building ArduPilot is a bit complicated, I've written a short script that uses Docker to build AP in a controlled environment.
Copy it from here, save it to a file called `docker_build.sh` in the root of the ArduPilot repo, and run it with `docker_build.sh <your board>`. Output files will be stored in `build/<yourboard>/bin/`, and you can flash them with the [INAV configurator](https://github.com/iNavFlight/inav-configurator/releases) by putting your board in DFU mode and uploading the `arduplane_with_bl.hex` file.
Here's the script:
```bash
#!/usr/bin/env bash
set -euox pipefail
if [ $# -ne 1 ]
then
echo "No board supplied, run as ./docker_build.sh <boardname> or ./docker_build.sh list"