https://sudreg.pravosudje.hr/ords/r/esudreg/public/podaci-o-poslovnom-subjektu?p28_sbt_mbs=070094563 lists company registered activities, including (autotranslate):

* Professional spatial planning tasks;
* Design, construction, use and removal of buildings;
* Construction supervision;

So I'd say they're the ones who are doing the work on e.g. building=construction (and who'd be tagged as builder=* on a building when it is completed). So it would be craft=builder