add timetzdata build tag to binary releases (#33463)

`timetzdata` is already used in the docker images, this includes them
for the binary release files too.

Related to #33235 (I don't have a windows machine setup to test this
though)

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

main_timezones.go

@@ -0,0 +1,16 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+//go:build windows
+
+package main
+
+// Golang has the ability to load OS's timezone data from most UNIX systems (https://github.com/golang/go/blob/master/src/time/zoneinfo_unix.go)
+// Even if the timezone data is missing, users could install the related packages to get it.
+// But on Windows, although `zoneinfo_windows.go` tries to load the timezone data from Windows registry,
+// some users still suffer from the issue that the timezone data is missing: https://github.com/go-gitea/gitea/issues/33235
+// So we import the tzdata package to make sure the timezone data is included in the binary.
+//
+// For non-Windows package builders, they could still use the "TAGS=timetzdata" to include the tzdata package in the binary.
+// If we decided to add the tzdata for other platforms, modify the "go:build" directive above.
+import _ "time/tzdata"