On Windows, this change includes the `FILE_FLAG_BACKUP_SEMANTICS` in
all calls to `CreateFile`.
Adding this flag allows is useful when rclone is running within a
security context that has `SeBackupPrivilege` and/or `SeRestorePrivilege`
token privileges enabled.
Without this flag, rclone cannot properly leverage special security
groups such as Backup Operators who possess the these privileges.
See: https://forum.rclone.org/t/rclone-sebackupprivilege-file-flag-backup-semantics/45339
See: https://github.com/rclone/rclone/pull/7877.
b778ec0142