add a default .o rule for easier debug
diff --git a/Rules.mak b/Rules.mak
index 53dd6a8..17e1367 100644
--- a/Rules.mak
+++ b/Rules.mak
@@ -350,4 +350,7 @@
 do_ar              = @$(disp_ar)        ; $(cmd_ar)
 do_elf2flt         = @$(disp_elf2flt)   ; $(cmd_elf2flt)
 
+%.o: %.c
+	$(compile.c)
+
 .PHONY: dummy