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/osbase/build/mkucode/main.go b/osbase/build/mkucode/main.go
index 58561e3..dcce5fb 100644
--- a/osbase/build/mkucode/main.go
+++ b/osbase/build/mkucode/main.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 // This assembles standalone microcode files into the format expected by the
 // Linux microcode loader. See
 // https://www.kernel.org/doc/html/latest/x86/microcode.html for further