libmedia_helper export headers

Have libmedia_helper export libmedia_headers so that future clients
won't need to explicitly include them.

Bug: 80076889
Test: sdk_google_iot_x86 builds.

Change-Id: Iac6e1237f10b461dbcd72370be843634aaff431d
diff --git a/media/libmedia/Android.bp b/media/libmedia/Android.bp
index ba7003a..8ff267f 100644
--- a/media/libmedia/Android.bp
+++ b/media/libmedia/Android.bp
@@ -32,6 +32,9 @@
         "libaudioclient_headers",
         "libaudio_system_headers",
     ],
+    export_header_lib_headers: [
+        "libmedia_headers",
+    ],
     clang: true,
 }