Step 1: Talk to him. Mention that the build is broken, and the last commit on it was his commit, so ask him what happened (it's important to not say "you broke the build!" because a) that's accusatory and b) perhaps his change wasn't actually the change that broke the build, e.g. maybe it was a configuration change, or maybe you forgot about a change you yourself made, etc, in which case you come off looking very abrasive and accusatory).
Step 2: If he is receptive to your statement, work with him to fix it and if he doesn't understand what went wrong, explain it to him. Explaining it to him will teach him how not to make the same mistake again. That's called mentorship and is very important among colleagues, particularly more experienced ones (towards less experienced ones). You will be looked on highly by your superiors if you can productively engage in mentorship.
Step 2a: In the extremely unlikely case that he is not receptive to your statement, then it's time to fight: Double-check your work to make absolutely sure he broke the build, then go to your manager and show him that the build is broken and that the colleague did it. Then it's the manager's problem, not yours, and that's where your responsibility ends.
Step 3: Next time this particular colleague breaks the build, rinse and repeat. If it happens a number of times and you feel it is a pattern of irresponsibility, then you can go to your manager and say "Hey Bob, you know Joe has broken the build a number of times and I've tried talking to him about it, but it just seems he doesn't care, mind talking to him about it?" or something like that. Don't go in aggressive or accusatory; make the issue about breaking the build, not about the colleague. Your manager will decide what the best course of action is from there.