[...]
> I'm primarily interested in kde, but cannot get past building pkgconfig
> which, though I seem to be able to install it, does not get picked up by
> subsequent packages relying upon it.

Check that

- pkgconfig is in your PATH

- PKG_CONFIG_DIR is pointing to the .pc files
(ususally in $PREFIX/lib/pkgconfig)


Just a shot...

--
Markus