Add libselinux keystore_key backend.

We add a new back end for SELinux based keystore2_key namespaces.
This patch adds the rump policy and build system infrastructure
for installing keystore2_key context files on the target devices.

Bug: 158500146
Bug: 159466840
Test: None
Change-Id: I423c9e68ad259926e4a315d052dfda97fa502106
Merged-In: I423c9e68ad259926e4a315d052dfda97fa502106
diff --git a/Android.mk b/Android.mk
index b667fd2..fa3a418 100644
--- a/Android.mk
+++ b/Android.mk
@@ -272,6 +272,7 @@
     build_sepolicy \
     plat_file_contexts \
     plat_file_contexts_test \
+    plat_keystore2_key_contexts \
     plat_mac_permissions.xml \
     plat_property_contexts \
     plat_property_contexts_test \