Because the version included in xtensa-lx106-elf-standalone.tar.gz needs
Python 2 (and pyserial for Python 2).
Signed-off-by: Damien George <damien@micropython.org>
The -Og optimisation level produces a more realistic build, gives a better
debugging experience, and generates smaller code than -O0, allowing debug
builds to fit in flash.
This commit also assigns variables in can.c to prevent warnings when -Og is
used, and builds a board in CI with DEBUG=1 enabled.
Signed-off-by: Damien George <damien@micropython.org>