cg-clean: fix argument processing

cg-clean was broken by the "robustified usage checks". This patch restores the old behavior, i.e. cg-clean reports errors if there is anything but switches on the command line. Empty arguments are rejected now as well.

index f680aee..1cc1ae8 100755
@@ -44,7 +44,7 @@ while optparse; do
 	fi
 done
 
-[ ${#ARGS[*]} -ge 1 ] || usage
+[ ${#ARGS[*]} = 0 ] || usage
 
 
 clean_dirs()

Regards,
Pavel Roskin