Freeciv

common/unittype.h, all current branches with just different numbers:

/* can be found in hut, global tech required */
#define SPECENUM_VALUE80 L_HUT_TECH
#define SPECENUM_VALUE80NAME N_("?unitflag:HutTech")

In fact, the unit is given in default.lua by

  local owner = unit.owner
  local type = find.role_unit_type('HutTech', owner)

while the method is

Unit_Type *api_find_role_unit_type(lua_State *L, const char *role_name,
                                   Player *pplayer)
{// ...
  if (pplayer) {
    return best_role_unit_for_player(pplayer, role_or_flag);
  }//...
}

that in fact requires that the player, not anybody, can build the unit. Either the comment should be corrected or we should give a unit using somehow find_a_unit_type(role, role_tech).