esp8266: Add module weak links; link time to utime.

esp8266/mpconfigport.h

@@ -14,6 +14,7 @@
 #define MICROPY_HELPER_REPL         (1)
 #define MICROPY_HELPER_LEXER_UNIX   (0)
 #define MICROPY_ENABLE_SOURCE_LINE  (1)
+#define MICROPY_MODULE_WEAK_LINKS   (1)
 #define MICROPY_PY_BUILTINS_STR_UNICODE (1)
 #define MICROPY_PY_BUILTINS_BYTEARRAY (1)
 #define MICROPY_PY_BUILTINS_MEMORYVIEW (1)
@@ -71,6 +72,9 @@ extern const struct _mp_obj_module_t utime_module;
     { MP_OBJ_NEW_QSTR(MP_QSTR_esp), (mp_obj_t)&esp_module }, \
     { MP_OBJ_NEW_QSTR(MP_QSTR_utime), (mp_obj_t)&utime_module }, \
 
+#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
+    { MP_OBJ_NEW_QSTR(MP_QSTR_time), (mp_obj_t)&utime_module }, \
+
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \