nxml-prefer-utf-16-little-to-big-endian-flag

nxml-prefer-utf-16-little-to-big-endian-flag is a variable defined in `nxml-mode.el'.
Its value is

nil

Documentation:
Non-nil means prefer little-endian to big-endian byte-order for UTF-16.
This is used only for saving a buffer; when reading the byte-order is
auto-detected. It may be relevant both when there is no encoding declaration
and when the encoding declaration specifies `UTF-16'.

You can customize this variable.