to build the app and produce an elf file run
bazel build //app --config 328p
to convert the app elf file to a hex file run
bazel build //app:hex --config 328p
to flash the app to your device run
bazel build //app:flash --config 328p
You need to have avr-gcc installed. Change toolchain/CROSSTOOL to fit your installation path. To add support for a different AVR CPU, add a new config to tools/bazel.rc.