When create a new `venv` on windows, sometimes an `UnicodeDecodeError` occurred.

It seems that, it is caused by the system module `site`.

In `Lib/site.py`, line 468::

        with open(virtual_conf) as f:
            for line in f:
                line = line.strip()

The file `virtual_conf` was open with encoding `gbk` which is my windows default encoding, but in fact, the file is an `utf-8` one, so i think it should be::

        with open(virtual_conf, encoding='utf-8') as f:
            for line in f:
                line = line.strip()

Already fixed in issue25185.