Clean up old files before generating them

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 1423099..7974f9b 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -651,6 +651,9 @@
 }
 
 pre_generate_files() {
+    # since make doesn't have proper dependencies, remove any possibly outdate
+    # file that might be around before generating fresh ones
+    make neat
     make generated_files
 }