Only need thread ID on macOS.
@@ -646,7 +646,9 @@ _papplMainloopRunServer(
// Temporary directory
const char *xdg_config_home = getenv("XDG_CONFIG_HOME");
// Freedesktop per-user config directory
+#ifdef __APPLE__
pthread_t tid; // Thread ID
+#endif // __APPLE__
// Create the system object...
