build: allow override of IMAGE_TAG

Change-Id: I23637f1c0d6d0e7cd45ad160209399cc9bf8b1a1
Reviewed-on: https://review.monogon.dev/c/monogon/+/1477
Tested-by: Jenkins CI
Reviewed-by: Leopold Schabel <leo@monogon.tech>
diff --git a/build/print-workspace-status.sh b/build/print-workspace-status.sh
index 07b5fd8..93fee03 100755
--- a/build/print-workspace-status.sh
+++ b/build/print-workspace-status.sh
@@ -19,7 +19,7 @@
 KUBERNETES_gitVersion="v1.24.2+mngn"
 
 # CI doesnt have the user set...
-IMAGE_TAG=${USER:-unknown}-$(date +%s)
+IMAGE_TAG=${IMAGE_TAG:-${USER:-unknown}-$(date +%s)}
 
 cat <<EOF
 KUBERNETES_gitCommit $(git rev-parse "HEAD^{commit}")