MacPorts can't recognize Xcode version properly
You need to run xcode-select --switch [path] as descriped here: https://stackoverflow.com/questions/9600615/xcode-stops-working-after-set-xcode-select-switch

And here is Apples documentation: https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/xcode-select.1.html