cmd/tests: Test that ErrorLevel is set to 9009 when unknown commands are encountered.

programs/cmd/tests/test_builtins.cmd

@@ -331,6 +331,9 @@ if not exist foo (
 )
 
 echo -----------Testing Errorlevel-----------
+rem WARNING: Do *not* add tests using ErrorLevel after this section
+should_not_exist 2> nul > nul
+echo %ErrorLevel%
 rem nt 4.0 doesn't really support a way of setting errorlevel, so this is weak
 rem See http://www.robvanderwoude.com/exit.php
 call :setError 1

programs/cmd/tests/test_builtins.cmd.exp

@@ -169,6 +169,7 @@ non-empty dir not removed
 recursive rmdir succeeded
 recursive rmdir succeeded
 -----------Testing Errorlevel-----------
+9009
 1
 errorlevel just right, good
 abc0def@or_broken@abc1def