selftests/nolibc: show failed run if test process crashes

The logic would not catch if the test process crashes and would
incorrectly report a "success" state. Fix this by looking for the final
"Total number of errors:" message and printing "failure" if it was not
seen.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://lore.kernel.org/r/20250709155512.971080-2-benjamin@sipsolutions.net


[Thomas: fix patch prefix]
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>