All windows conda build jobs are failing

[NicolasHug]

E.g. in #8647. Seems to be an infra issue. Hopefully solved by pytorch/test-infra#5646

    Traceback (most recent call last):
      File "C:\Jenkins\Miniconda3\lib\site-packages\conda\exception_handler.py", line 18, in __call__
        return func(*args, **kwargs)
      File "C:\Jenkins\Miniconda3\lib\site-packages\conda\cli\main.py", line 84, in main_subshell
        exit_code = do_call(args, parser)
      File "C:\Jenkins\Miniconda3\lib\site-packages\conda\cli\conda_argparse.py", line 176, in do_call
        result = plugin_subcommand.action(getattr(args, "_args", args))
      File "C:\Jenkins\Miniconda3\lib\site-packages\conda_build\plugin.py", line 15, in build
        from .cli.main_build import execute
      File "C:\Jenkins\Miniconda3\lib\site-packages\conda_build\cli\main_build.py", line 19, in <module>
        from .. import api, build, source, utils
      File "C:\Jenkins\Miniconda3\lib\site-packages\conda_build\api.py", line 23, in <module>
        from .config import DEFAULT_PREFIX_LENGTH as _prefix_length
      File "C:\Jenkins\Miniconda3\lib\site-packages\conda_build\config.py", line 23, in <module>
        from .utils import (
      File "C:\Jenkins\Miniconda3\lib\site-packages\conda_build\utils.py", line 49, in <module>
        import libarchive
      File "C:\Jenkins\Miniconda3\lib\site-packages\libarchive\__init__.py", line 1, in <module>
        from .entry import ArchiveEntry
      File "C:\Jenkins\Miniconda3\lib\site-packages\libarchive\entry.py", line 6, in <module>
        from . import ffi
      File "C:\Jenkins\Miniconda3\lib\site-packages\libarchive\ffi.py", line 26, in <module>
        libarchive = ctypes.cdll.LoadLibrary(libarchive_path)
      File "C:\Jenkins\Miniconda3\lib\ctypes\__init__.py", line 452, in LoadLibrary
        return self._dlltype(name)
      File "C:\Jenkins\Miniconda3\lib\ctypes\__init__.py", line 364, in __init__
        if '/' in name or '\\' in name:
    TypeError: argument of type 'NoneType' is not iterable