fix: mark the C extension as safe for free-threading #1799

Author: nedbat

coverage/ctracer/module.c

@@ -31,6 +31,10 @@ PyInit_tracer(void)
         return NULL;
     }
 
+#ifdef Py_GIL_DISABLED
+    PyUnstable_Module_SetGIL(m, Py_MOD_GIL_NOT_USED);
+#endif
+
     if (CTracer_intern_strings() < 0) {
         return NULL;
     }