}
    bool supportsStep(Step::ptr step)
    {
        if (systemTypes.find(step->drv.platform) == systemTypes.end()) return false;
        // FIXME: check features
        return true;

            printMsg(lvlInfo, format("aborting GC'ed build %1%") % build->id);

            printMsg(lvlError, format("aborting GC'ed build %1%") % build->id);

            continue;
        }
        /* If any step has an unsupported system type, then fail the
           build. */
        bool allSupported = true;
        for (auto & r : newRunnable) {
            bool supported = false;
            {
                auto machines_(machines.lock()); // FIXME: use shared_mutex
                for (auto & m : *machines_)
                    if (m->supportsStep(r)) { supported = true; break; }
            }
            if (!supported) { allSupported = false; break; }
        }

        if (!allSupported) {
            printMsg(lvlError, format("aborting unsupported build %1%") % build->id);
            pqxx::work txn(conn);
            txn.parameterized
                ("update Builds set finished = 1, busy = 0, buildStatus = $2, startTime = $3, stopTime = $3, errorMsg = $4 where id = $1")
                (build->id)
                ((int) bsAborted)
                (time(0))
                ("unsupported system type").exec();
            txn.commit();

        if (!has(machine->systemTypes, step->drv.platform)) continue;
        // FIXME: check features

        if (!machine->supportsStep(step)) continue;