Upgrade debugging, fix upgrade on ARM (fixes #482)

upgrade/debug.go

@@ -0,0 +1,17 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+// All rights reserved. Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package upgrade
+
+import (
+	"os"
+	"strings"
+
+	"github.com/syncthing/syncthing/logger"
+)
+
+var (
+	debug = strings.Contains(os.Getenv("STTRACE"), "upgrade") || os.Getenv("STTRACE") == "all"
+	l     = logger.DefaultLogger
+)