Paths with spaces not handled for Python paths

Even when the environment variables `LIBDIR`, `GOPY_LIBDIR`, `LIBRARY` and `GOPY_PYLIB` are properly set and surrounded with quotes (even tried double quoting with the inner pair escaped) spaces in the path are not properly handled. I had to move my python installation from `C:\Program Files\Python3` up to `C:\Python3` to get a package to build.

未指定文件或测试。首先，在 Python 安装于包含空格的路径下的 Windows 环境中，使用列出的环境变量复现 package build。跟踪这些变量在 build 期间的读取和传递方式；无需移动 Python 安装即可完成 package build，即表示完成。

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