admin: add build tags to "About"

build tags like e2ee and external are now included in the about page.

notray.go

@@ -1,9 +1,12 @@
+//go:build !tray
 // +build !tray
 
 package main
 
 var TRAY = false
 
+func BuildTagsTray() {}
+
 func RunTray() {}
 
 func QuitTray() {}