As stated in #2408 (comment) make flash (using the unified OpenOCD script from #2408) is currently not working for the SAMR21 - at least on ArchLinux. (Neither with the AUR version of OpenOCD nor with a fresh compiled from current git HEAD.) Putting an exit at the end of the program command or adding a shutdown command at the end helps, but leads to 1 as an exit code indicating an error - but I don't know why, because flashing seems to work correctly.