srcdir != builddir problems with docs

[Rolf Magnus]

It seems that the KDE documentation doesn't work with srcdir != builddir 
anymore. When I compile kdebase e.g., I get:

warning: failed to load external entity "kdmrc-ref.docbook"
Entity: line 929: error: Failure to process entity kdmrc-ref
&kdmrc-ref;
           ^
Entity: line 929: error: Entity 'kdmrc-ref' not defined
&kdmrc-ref;
           ^
unable to parse ../../../kdebase/doc/kdm/index.docbook
make: *** [index.cache.bz2] Error 1

kdmrc-ref.docbook is in the srcdir, and when I copy it to the builddir, it 
compiles, but I get a similar error for the next file. Same in many other KDE 
modules. Any solutions?