$ cd /Applications/Xcode.app/Contents/MacOS/
$ sudo unsign Xcode
$ sudo mv Xcode Xcode.signed
$ sudo ln -s Xcode.unsigned Xcode
$ ls -al
total 64
drwxr-xr-x 5 gk staff 170 Oct 25 14:27 .
drwxr-xr-x 16 gk staff 544 Oct 15 06:22 ..
lrwxr-xr-x 1 gk staff 14 Oct 25 14:27 Xcode -> Xcode.unsigned
-rwxr-xr-x 1 gk staff 18528 Oct 15 06:30 Xcode.signed
-rwxr-xr-x 1 gk staff 18528 Oct 25 14:26 Xcode.unsigned