Andreas Pakulat authored Jun 06, 2013 and Sven Brauch committed Jun 13, 2013

The find-module already sets up the includedir to be
<prefix>/include/kasten2/okteta1 etc. so using the relative path here as
well breaks builds where okteta is installed in its own prefix and hence
there's no -I<prefix>/include on the compiler commandline.

Cherry-picked (by Sven) to 4.5 in order to fix build.kde.org