Mostly empty unit tests -- added mgos_mock to be able to run unit tests on x86_64

unittest/main.c

@@ -0,0 +1,8 @@
+#include "test.h"
+
+int main() {
+  LOG(LL_INFO, ("test_widget"));
+  test_widget();
+  test_screen();
+  return 0;
+}