Add fsverity release cert

The release cert helps verifying CTS in a release build.

Bug: 153112812
Test: build, reboot, see a new key in /proc/keys
Change-Id: I6d8f4af6b1b0c023b668e81b7a1c71c7583d93d9
Merged-In: I6d8f4af6b1b0c023b668e81b7a1c71c7583d93d9
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index 70dd80e..4f1c185 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -86,6 +86,7 @@
     framework-res \
     framework-sysconfig.xml \
     fsck_msdos \
+    fsverity-release-cert-der \
     fs_config_files_system \
     fs_config_dirs_system \
     group_system \