In trying to write a non-recursive make, I have the following block:

```
dir := $(ROOT)/libs/libA/
include $(dir)/rules.mk

dir := $(ROOT)/libs/libB/
include $(dir)/rules.mk

dir := $(ROOT)/libs/libC/
include $(dir)/rules.mk

```

This is obviously unnecessary repetitive. How can I write a macro to collapse that all so that I just have to provide `libA`, `libB`, and `libC`? I need to also set `dir` before each `include`.