Enable windows target

`//tools/apksig` build targets will soon depend
on this, and windows must be enabled (transitively)
on all dependencies.

Bug: 319296492
Test: TH
Change-Id: I11d5acaecb20d7de4797ddc418fb4714b18057c3
diff --git a/annotations/Android.bp b/annotations/Android.bp
index 05b9e29..7808fa8 100644
--- a/annotations/Android.bp
+++ b/annotations/Android.bp
@@ -36,4 +36,9 @@
 
     srcs: ["src/**/*.java"],
     java_resource_dirs: ["src"],
+    target: {
+        windows: {
+            enabled: true,
+        },
+    },
 }