Adding METADATA file to selinux

Test: TreeHugger
Change-Id: I4ff048c7adf2fd07431590d04f56ae6d34cbf603

METADATA

@@ -1,3 +1,19 @@
+# This project was upgraded with external_updater.
+# Usage: tools/external_updater/updater.sh update selinux
+# For more info, check https://cs.android.com/android/platform/superproject/+/master:tools/external_updater/README.md
+
+name: "selinux"
+description: "SELinux is a flexible Mandatory Access Control (MAC) system built into the Linux Kernel."
 third_party {
+  url {
+    type: GIT
+    value: "https://github.com/SELinuxProject/selinux.git"
+  }
+  version: "3.5-rc2"
   license_type: RESTRICTED
+  last_upgrade_date {
+    year: 2023
+    month: 2
+    day: 16
+  }
 }