always tee test linuxkit run to tty, so if it gets stuck, we see why (#4107)

Signed-off-by: Avi Deitcher <avi@deitcher.net>

test/cases/020_kernel/013_config_5.10.x/test.sh

@@ -18,7 +18,7 @@ trap clean_up EXIT
 
 # Test code goes here
 linuxkit build --format kernel+initrd --name "${NAME}" test.yml
-RESULT="$(linuxkit run ${NAME})"
+RESULT="$(linuxkitrun ${NAME})"
 echo "${RESULT}" | grep -q "suite PASSED"
 
 exit 0