make sure the non-ref test are always executed in the same order

by piping the output od find by sort in the test/Makefile.

src/test/Makefile

@@ -3,9 +3,9 @@ LC=../lus2lic -vl 3
 NL="----------------------------------------------------------------------\\n"
 
 
-OK_LUS=$(shell find should_work -name "*.lus" -print)
+OK_LUS=$(shell find should_work -name "*.lus" -print | sort -n)
 
-KO_LUS=$(shell find should_fail -name "*.lus" -print)
+KO_LUS=$(shell find should_fail -name "*.lus" -print | sort -n)
 
 test:
 	echo "Non-regression tests" > test_ok.res