I noticed that seL4/libsel4 was dependent upon libc and so I created a patch (https://github.com/winksaville/seL4/commit/fc91a1f68c054fdb41aaa42a7b56a80f481b68b2) which removes the dependency. If there is interest I can submit a pull request, and of course will make any changes deemed necessary to make it suitable for acceptance.