Since the switch to CMAKE we are not running the WebKit2 C API tests, because now there are built in several binaries and non of them starts with "Test" prefix. We should either rename the binaries to have a Test prefix, or remove the restriction for non WebKit2Gtk tests (we use the Test prefix in WebKit2Gtk tests to avoid trying to run other binaries like the a11y test server, or the remote inspector server as tests).
This should be fixed now by r168574