Change intermediate data file extension to .datax
diff --git a/tests/Makefile b/tests/Makefile
index e8091cc..e344635 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -205,9 +205,9 @@
 
 clean:
 ifndef WINDOWS
-	rm -rf $(APPS) *.c *.data TESTS
+	rm -rf $(APPS) *.c *.datax TESTS
 else
-	del /Q /F *.c *.exe *.data
+	del /Q /F *.c *.exe *.datax
 	rmdir /Q /S TESTS
 endif