IdeIntf package was refactored, non-GUI parts were moved to a new BuildIntf package.
Commit r62795 by Mattias (although I did the actual split).
Rebuilding the sources after r62795 using a Lazarus executable built before it gives an error. The old IDE does not know where the BuildInf package is. The easiest cure is to open components/buildide.lpk in the IDE.