There's 2 problems here:
* The rpath check considers '/opt/kde4/lib' to be an invalid rpath. I'm not
sure what is supposed to be "invalid" about that rpath. It's not a standard
search path, and it _is_ an absolute path. So we'll have to disable the rpath
checks, but they really ought to be fixed.
* KDE is putting in rpaths to '/lib' and '/usr/local/lib'. This is bad. I'm not
sure where the '/usr/local/lib' is coming from (none of the linked libraries
should be there!), and '/lib' is also bad (there's probably a filter
for '/usr/lib', but not plain '/lib' in cmake). A possible workaround for this
issue would be to use -DCMAKE_DISABLE_RPATH=TRUE as you did and to add:
-Wl,--rpath,/opt/kde4/lib
to the LDFLAGS instead (so we'd set the rpath manually rather than
automatically).