Add #ifdef MS_WINDOWS

Doc/whatsnew/3.13.rst

@@ -942,7 +942,8 @@ Removed
   * ``Py_SetProgramName()``: set :c:member:`PyConfig.program_name` instead.
   * ``Py_SetPythonHome()``: set :c:member:`PyConfig.home` instead.
   * ``Py_SetStandardStreamEncoding()``: set :c:member:`PyConfig.stdio_encoding`
-    instead, and set also maybe :c:member:`PyConfig.legacy_windows_stdio`.
+    instead, and set also maybe :c:member:`PyConfig.legacy_windows_stdio` (on
+    Windows).
   * ``_Py_SetProgramFullPath()``: set :c:member:`PyConfig.executable` instead.
 
   Use the new :c:type:`PyConfig` API of the :ref:`Python Initialization

Programs/_testembed.c

@@ -237,9 +237,11 @@ static void check_stdio_details(const wchar_t *encoding, const wchar_t *errors)
     if (errors) {
         config_set_string(&config, &config.stdio_errors, errors);
     }
+#ifdef MS_WINDOWS
     // gh-106659: On Windows, don't use _io._WindowsConsoleIO which always
     // announce UTF-8 for sys.stdin.encoding.
     config.legacy_windows_stdio = 1;
+#endif
     config_set_program_name(&config);
     init_from_config_clear(&config);