starting August 4th, i.e. Monday in 2 weeks, CMake >= 2.6.0 will be required to build KDE from svn trunk, which will become KDE 4.2 in a few months.
So please update your CMake.
In case there are no distribution packages yet, you can get the sources here:
or the binary package, which should work on about every Linux distribution:
(just unpack it to any place you like, it will work).