rust: Visibility exports for bindgen

We are now default restricting bindgen visibility to subpackages. This
change is part of a set of changes adding explicit visibility for
bindgen libraries which are already being used elsewhere.

* If these visibility rules are to allow access by the safe bindings
  library which lives elsewhere in the codebase, no action is needed.
* If safe bindings do not exist, and you own this library, now is a good
  time to think about producing them and transitioning your (now
  enumerated) client list.
* If safe bindings exist, but there is a surprise client of the raw
  bindings on this list, now is a good time to talk to them about why
  they don't want to use your safe bindings.

Bug: 166332519
Test: m
Change-Id: I3f731ac41b36d28a3f86d22133bf57f2721e9baa
diff --git a/libs/avb_bindgen/Android.bp b/libs/avb_bindgen/Android.bp
index 1e62864..6dc16e8 100644
--- a/libs/avb_bindgen/Android.bp
+++ b/libs/avb_bindgen/Android.bp
@@ -7,6 +7,7 @@
     host_supported: true,
     wrapper_src: "bindgen/avb.h",
     crate_name: "avb_bindgen",
+    visibility: ["//packages/modules/Virtualization:__subpackages__"],
     source_stem: "bindings",
     bindgen_flags: [
         "--size_t-is-usize",