I'm working on a free software (bsd license) project with others. We're searching for a system that check out our source code (svn) and build it also as test it (unit tests with Check / other tools).
It should have a webbased interface and generate reports.
I hope we don't have to write such a system from null by ourselves...
You surely do not have to code this yourself - there are a lot of continuous integration systems which are able to check out source code from systems such as SVN and they are generally easy to extend with your own tasks, so running custom test scripts/programs should not be a problem.
While these CI systems are probably not written in C, this does not matter, since they just need to be able to access and compile your source code, for which they will use an external compiler anyways.
Just to list some of the well known CI tools:
You might also be interested in other questions on Stack Overflow tagged as continuous-integration. :)