Move EXTRA_GENERATED mentions to a separate line

This makes reconciliation with other branches that don't have
it (mbedtls, backports) easier.
diff --git a/programs/Makefile b/programs/Makefile
index f56df5f..250c648 100644
--- a/programs/Makefile
+++ b/programs/Makefile
@@ -246,7 +246,8 @@
 
 clean:
 ifndef WINDOWS
-	rm -f $(APPS) $(EXTRA_GENERATED)
+	rm -f $(APPS)
+	rm -f $(EXTRA_GENERATED)
 	-rm -f test/cpp_dummy_build$(EXEXT)
 else
 	if exist *.o del /Q /F *.o