microdroid: Add support for extra apk files

extra_apk_file is a new label only for APK files passed to microdroid.
microdroid_manager will create directories under /mnt/extra-apk/, and
zipfuse will mount APK block devices to the directories.

Currently only payload can read the files.

Bug: 205224817
Test: manually edit vm config and see APK files mounted
Change-Id: Ie5afb3156f22bb18979ec70904be675e8ff285a7
diff --git a/microdroid/system/private/file.te b/microdroid/system/private/file.te
index cbbd379..18fa8bb 100644
--- a/microdroid/system/private/file.te
+++ b/microdroid/system/private/file.te
@@ -4,6 +4,7 @@
 allow cgroup_rc_file tmpfs:filesystem associate;
 allow debugfs_type { debugfs debugfs_tracing debugfs_tracing_debug }:filesystem associate;
 allow dev_type tmpfs:filesystem associate;
+allow extra_apk_file zipfusefs:filesystem associate;
 allow file_type labeledfs:filesystem associate;
 allow file_type tmpfs:filesystem associate;
 allow file_type rootfs:filesystem associate;