Allow apexd to relabel files in /data/apex/decompressed

We have created a new directory called /data/apex/decompressed. All
files under this directory will have staging_data_file label, but
the directory itself needs to have apex_data_file label. This is
because apexd needs to write inside this directory and we don't want
to give apexd write access to staging_data_file label.

When a file is written under this directory, it gets its parent's label.
So we need to restore the proper labeling. Hence, we are allowing apexd
labeling permissions.

Bug: 172911820
Test: atest ApexCompressionTests#testCompressedApexIsActivated
Change-Id: I0a910fa5591b2aace70804701545eb4ac510ec24
diff --git a/private/file_contexts b/private/file_contexts
index 7aeba99..2a76712 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -518,6 +518,7 @@
 /data/apex(/.*)?		u:object_r:apex_data_file:s0
 /data/apex/active/(.*)?		u:object_r:staging_data_file:s0
 /data/apex/backup/(.*)?		u:object_r:staging_data_file:s0
+/data/apex/decompressed/(.*)?    u:object_r:staging_data_file:s0
 /data/app(/.*)?                       u:object_r:apk_data_file:s0
 # Traditional /data/app/[packageName]-[randomString]/base.apk location
 /data/app/[^/]+/oat(/.*)?                u:object_r:dalvikcache_data_file:s0