#71819 Broke windows bootstrap.

[crlf0710]

In #71819, this code is added in bootstrap.py

    required = not sys.platform == 'win32'
    ostype = require(["uname", "-s"], exit=required).decode(default_encoding)
    cputype = require(['uname', '-m'], exit=required).decode(default_encoding)

And on windows, this error is emitted:

  File "L:\ThirdParty\rust\rust-workdir\src\bootstrap\bootstrap.py", line 184, in default_build_triple
    ostype = require(["uname", "-s"], exit=required).decode(default_encoding)
AttributeError: 'NoneType' object has no attribute 'decode'

@jyn514 cc @Mark-Simulacrum

[Mark-Simulacrum]

This is fixed by #71964