Add apex_available for AdServices

This CL enables apex availability for AdServices, which depends on this
package via build targets being added in tflite-support.

Test: m
Bug: 228842813
Change-Id: Ia66ef12c6632d5f69cd58248604afca2357ec87a
diff --git a/Android.bp b/Android.bp
index d852d62..912cec0 100644
--- a/Android.bp
+++ b/Android.bp
@@ -133,6 +133,10 @@
     sdk_version: "9",
 
     stl: "c++_static",
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.adservices",
+    ],
 }
 
 // C++ lite library for the platform and host.