Don't build build.go on go get

build.go

@@ -1,3 +1,9 @@
+// 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.
+
+// +build ignore
+
 package main
 
 import (