All of the versions in portage don't specifiy this dependancy despite it being required. Configuring will error on "glib-config" not being found. To fix this, please update all of the ebuilds to have the following: DEPEND="=net-im/jabberd-1.4* =dev-libs/glib-1*"
Confirmed here, fix does of course fix it.
Still not fix in the eportage tree...
Fixed in the tree, thanks for help.