Fix another way field factory blocks regular build options.

Units that can be blueprinted were always blocked if they weren't
the currently selected blueprint. This applied even if the unit was
on the standard list of buildees.

For example, trying to add Athena back to the global list of things
available for all cons left Support Comm unable to build it until
it was blueprinted from a strider hub.

Author: sprunk

LuaRules/Gadgets/unit_field_factory.lua

@@ -94,6 +94,16 @@ local factoryDefIDs = {}
 local fieldBuildOpts = {}
 do
 	local alreadyAdded = {}
+
+	-- FIXME: assumes all constructors have the same buildlists
+	local buildableDirectly = VFS.Include("gamedata/buildoptions.lua")
+	for i = 1, #buildableDirectly do
+		local ud = UnitDefNames[buildableDirectly[i]]
+		if ud then
+			alreadyAdded[ud.id] = true
+		end
+	end
+
 	for i = 1, #factories do
 		local factoryName = factories[i]
 		local ud = UnitDefNames[factoryName]