treewide: add license header and enable haslicense linter

Change-Id: I873a8d4082d75e8f813d8a726a41187eea7a065e
Reviewed-on: https://review.monogon.dev/c/monogon/+/3825
Tested-by: Jenkins CI
Reviewed-by: Leopold Schabel <leo@monogon.tech>
diff --git a/build/analysis/noioutil/noioutil.go b/build/analysis/noioutil/noioutil.go
index b98a921..69223b1 100644
--- a/build/analysis/noioutil/noioutil.go
+++ b/build/analysis/noioutil/noioutil.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 // Package noioutil contains a Go analysis pass designed to prevent use of the
 // deprecated ioutil package for which a tree-wide migration was already done.
 package noioutil