Patch also PySys_SetArgv()

Modify also PySys_SetArgv() to use PyConfig.isolated when Python is
initialized.

Author: vstinner

Python/sysmodule.c

@@ -4540,9 +4540,16 @@ PySys_SetArgvEx(int argc, wchar_t **argv, int updatepath)
 void
 PySys_SetArgv(int argc, wchar_t **argv)
 {
+    int isolated = 0;
+    PyThreadState *tstate = PyThreadState_GetUnchecked();
+    if (tstate != NULL) {
+        const PyConfig *config = &tstate->interp->config;
+        isolated = config->isolated;
+    }
+
 _Py_COMP_DIAG_PUSH
 _Py_COMP_DIAG_IGNORE_DEPR_DECLS
-    PySys_SetArgvEx(argc, argv, Py_IsolatedFlag == 0);
+    PySys_SetArgvEx(argc, argv, isolated == 0);
 _Py_COMP_DIAG_POP
 }