Modern MSVC or Windows versions don't support big-endian, so it's
unnecessary to consider architectures when using it.
This also makes ARM64 MSVC builds succeed.
Helped-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Daniel Gurney <dgurney99@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>