Make libarect buildable for native_bridge

Also make headers available for RenderScript.

Bug: http://b/153609531

Test: m libarect.native_bridge
Change-Id: Iee387d19d167d8b90f4bf3fae7869ea370025b9a
diff --git a/libs/nativewindow/Android.bp b/libs/nativewindow/Android.bp
index 894f45a..a756bc7 100644
--- a/libs/nativewindow/Android.bp
+++ b/libs/nativewindow/Android.bp
@@ -25,6 +25,8 @@
     name: "libnativewindow_headers",
     export_include_dirs: ["include"],
     vendor_available: true,
+    // TODO(b/153609531): remove when no longer needed.
+    native_bridge_supported: true,
     min_sdk_version: "29",
 }