bpo-36301: Fix _PyPreConfig_Read() compiler warning (GH-12695)

Initialize init_utf8_mode earlier to fix a compiler warning.

Author: vstinner

Python/preconfig.c

@@ -720,17 +720,18 @@ _PyPreConfig_Read(_PyPreConfig *config, const _PyArgv *args)
     _Py_SetLocaleFromEnv(LC_CTYPE);
 
     _PyPreCmdline cmdline = _PyPreCmdline_INIT;
+    int init_utf8_mode = Py_UTF8Mode;
+#ifdef MS_WINDOWS
+    int init_legacy_encoding = Py_LegacyWindowsFSEncodingFlag;
+#endif
+
     if (args) {
         err = _PyPreCmdline_SetArgv(&cmdline, args);
         if (_Py_INIT_FAILED(err)) {
             goto done;
         }
     }
 
-    int init_utf8_mode = Py_UTF8Mode;
-#ifdef MS_WINDOWS
-    int init_legacy_encoding = Py_LegacyWindowsFSEncodingFlag;
-#endif
     int locale_coerced = 0;
     int loops = 0;