Allow `otapreopt_chroot` to use a flattened Runtime APEX package.

- Allow (again) `otapreopt` (running as `postinstall_dexopt`) to
  execute `dex2oat` from `/postinstall` -- this is for the case where
  it is located in a flattened Runtime APEX in
  `/postinstall/system/apex`.
- Allow `dex2oat` to read directories under `/postinstall`.
- Allow `otapreopt_chroot` to unmount flattened APEX packages under
  `/postinstall/system/apex` (which are bind-mounted in
  `/postinstall/apex`).

Test: A/B OTA update test (asit/dexoptota/self_full).
Bug: 127543974
Bug: 123684826
Bug: 113373927
Change-Id: Ie023ee5c64989ea071e1683f31073a70c93cac18
diff --git a/private/otapreopt_chroot.te b/private/otapreopt_chroot.te
index ba85678..efde869 100644
--- a/private/otapreopt_chroot.te
+++ b/private/otapreopt_chroot.te
@@ -11,6 +11,9 @@
 # APEX packages in /postinstall/apex.
 allow otapreopt_chroot block_device:dir search;
 allow otapreopt_chroot labeledfs:filesystem { mount unmount };
+# This is required to unmount flattened APEX packages under
+# /postinstall/system/apex (which are bind-mounted in /postinstall/apex).
+allow otapreopt_chroot postinstall_file:filesystem unmount;
 # Mounting /vendor can have this side-effect. Ignore denial.
 dontaudit otapreopt_chroot kernel:process setsched;