https://docs.python.org/3/using/cmdline.html#cmdoption-P

https://github.com/RustPython/RustPython/pull/4537/files#diff-cb42fd26146ec61cb2242243494a9f314667a9a39153ad17e37465ff5a8a8000R536

• add sys.flags.safe_path add sys.flags and sys.int_info #4568
• add command line parameter -P to set flag
• use environment variable PYTHONSAFEPATH to set flag
• actual implementation of safe_path

I didn't check the actual implementation, but other 3 tasks are easy tasks