Did they adjust for precession?
Great question. Some estimates of the creation of the Great Sphinx puts it as far back as 10,000 BC, so the axis of the Earth has moved considerably in that time.
Nice question! A similar problem was pointed out back at the time of Hawkins' book "Stonehenge Decoded" (I think that was the crock that got the grossly misnamed "Most Ancient Order of Druids" annual shindig started; it's an interesting read though; these fake druids started in the late 18th c). The Sun -- which sort of rolls up one side of the "heel stone" on solstice day -- would have been even more off the mark back when that phase of the monument is believed to have been constructed.