path_error() uses GetLastError() on Windows, but some os functions
are implemented via CRT APIs which report errors via errno.
This may result in raising OSError with invalid error code (such
as zero).

Introduce posix_path_error() function and use it where appropriate.
(cherry picked from commit 83460311)
Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>