Add windows/arm64 KMS plugin asset stub so all release targets build

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

plugins/kms/assets/windows/arm64/README.md

@@ -0,0 +1,3 @@
+This directory contains assets for windows amd64 kms plugins. This file 
+in particular exists so that the Go embed package does not throw errors 
+when importing this module outside of the main tree.

plugins/kms/assets_windows_arm64.go

@@ -0,0 +1,13 @@
+// Copyright IBM Corp. 2020, 2026
+// SPDX-License-Identifier: MPL-2.0
+
+package kms_plugin_assets
+
+import (
+	"embed"
+)
+
+// content is our static kms plugin content.
+//
+//go:embed assets/windows/arm64
+var content embed.FS