When you post to Code Review, there's always an implicit question:
How can my code be improved?
If you have specific aspects that you would like to be improved, then you can mention them in the question - as many as you like. Reviewers are always free to comment on anything they find in the code, even if you haven't drawn attention to it like that.
If your specific questions would cover everything that reviewers might consider anyway, then you could consider not giving any guidance to the aspects of interest, and just hope for wide-ranging reviews. I would probably take that approach initially, improve the code based on answers received, then post a second review request with the new code and ask about any aspects that weren't addressed in the first reviews.
Before you post your code for review, it's worth looking through a few of the existing makefile questions, as you may well learn things from those that you can apply to your own code. That will then allow reviewers to focus on the things that are specific to your Makefile, rather than repeating common problems.
An extra hint: don't Accept the first answer you get, as that indicates that you don't need more reviews. Wait a few days to see if you get several answers that address the different aspects of your code.