Doha is the longest I've come across, and rumour amongst the builders was that one-upmanship was part of the design process.
The only other very very long one I know of in the area is the first of the runways at Jebel Ali ... Dubai World Central ... Al Maktoum International Airport (JXB) which is reportedly 4500m long.
There is a new airbase in the region for which construction tenders are being submitted at present - not sure of the name or length but will see what I can find.