Add luacheck to check builtin (#7895)

builtin/game/item.lua

@@ -206,7 +206,6 @@ function core.get_node_drops(node, toolname)
 	-- Extended drop table
 	local got_items = {}
 	local got_count = 0
-	local _, item, tool
 	for _, item in ipairs(drop.items) do
 		local good_rarity = true
 		local good_tool = true
@@ -614,15 +613,10 @@ function core.node_dig(pos, node, digger)
 	end
 
 	-- Run script hook
-	local _, callback
 	for _, callback in ipairs(core.registered_on_dignodes) do
 		local origin = core.callback_origins[callback]
 		if origin then
 			core.set_last_run_mod(origin.mod)
-			--print("Running " .. tostring(callback) ..
-			--	" (a " .. origin.name .. " callback in " .. origin.mod .. ")")
-		else
-			--print("No data associated with callback")
 		end
 
 		-- Copy pos and node because callback can modify them