Try this:
function saveFile(strFullPath, strContent) {
var fso = new ActiveXObject("Scripting.FileSystemObject");
var utf8Enc = new ActiveXObject("Utf8Lib.Utf8Enc");
var flOutput = fso.CreateTextFile(strFullPath, true); //true for overwrite
flOutput.BinaryWrite(utf8Enc.UnicodeToUtf8(strContent));
flOutput.Close();
}