Exit code of `./pl --run-tests` is the number of failed tests.

src/pebblisp.c

@@ -771,8 +771,7 @@ int main(int argc, const char* argv[])
     setGlobal(&env);
 
     if (argc == 2 && strcmp(argv[1], "--run-tests") == 0) {
-        runTests();
-        return 0;
+        return runTests();
     }
 
     struct sigaction action;