Allow priv_app read access to /data/app-staging directory

During staged installation, we no longer create duplicate sessions for
verification purpose. Instead, we send the original files in
/data/app-staging folder to package verifiers for verification. That
means, Phonesky needs access to /data/app-staging folder to be able to
verify the apks inside it.

Bug: 175163376
Test: atest StagedInstallTest#testPlayStoreCanReadAppStagingDir
Test: atest StagedInstallTest#testAppStagingFolderCannotBeReadByNonPrivApps
Change-Id: I5cbb4c8b7dceb63954c747180b39b4a21d2463af
diff --git a/private/priv_app.te b/private/priv_app.te
index 07ed6c7..6a60cd1 100644
--- a/private/priv_app.te
+++ b/private/priv_app.te
@@ -156,6 +156,8 @@
 # Required for Phonesky to be able to read APEX files under /data/apex/active/.
 allow priv_app apex_data_file:dir search;
 allow priv_app staging_data_file:file r_file_perms;
+# Required for Phonesky to be able to read staged files under /data/app-staging.
+allow priv_app staging_data_file:dir r_dir_perms;
 
 # allow priv app to access the system app data files for ContentProvider case.
 allow priv_app system_app_data_file:file { read getattr };