Hi there. I've made a sample public project you can check out to see an example of running C code [0]. I just wrote a shell script that compiles my C code and then executes the resulting binary. Then I tell Domino to run my shell script. Voila. Let me know if you have any questions.
We allude to this in our FAQ ("What if I want to run C++ code...") but we'll update the docs to make the specific instructions more clear.