treewide: dynamically generate copyright line

A copyright line with hardcoded year was shown in various places of the
UI. Instead, take the year from the commit date.

Change-Id: I424d6c5b3aff34fe4479c37f30f9ea280b7eb4af
Reviewed-on: https://review.monogon.dev/c/monogon/+/4168
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/build/BUILD.bazel b/build/BUILD.bazel
index 20cfd57..3708a0b 100644
--- a/build/BUILD.bazel
+++ b/build/BUILD.bazel
@@ -12,6 +12,7 @@
         "KUBERNETES_gitCommit",
         "KUBERNETES_gitTreeState",
         "KUBERNETES_buildDate",
+        "MONOGON_copyright",
     ],
     visibility = ["//visibility:public"],
 )