Added arduino-nano to BOARD_INSUFFICIENT_MEMORY/BOARD_BLACKLIST following suit of how arduino-uno is marked, as arduino-nano is mostly an Uno in a different form factor.
Expected result
You should see the following sequence at the console
main: starting main: exiting 2nd: starting 3rd: starting 3rd: exiting 2nd: exiting 4th: starting 4th: exiting