nshlib/[cd|ls|pwd]: add support for local CWD(Current working directory)

This PR will still allow basic shell operations such as cd/ls/pwd to be used even when the environment is disabled.

Signed-off-by: chao an <anchao@lixiang.com>

nshlib/nsh_console.h

@@ -150,6 +150,12 @@ struct nsh_vtbl_s
   /* Ctrl tty or not */
 
   bool isctty;
+
+  /* Current working directory */
+
+#ifdef CONFIG_DISABLE_ENVIRON
+  char cwd[PATH_MAX];
+#endif
 };
 
 /* This structure describes a console front-end that is based on stdin and