Add /persist symlink to mainline_arm64

Since /persist is a SoC specfic symlink, it must not be included in
the root directory. For this reason, we already moved the directory
under /mnt/vendor. However, there are still many modules that are
using the old path /persist.
Until we clear all these violations, we need to have the symlink in
the root directory.

Bug: 143732851
Test: build and check boot and basic functions
Change-Id: Iaee28ba29f79f1c286e090f97173e3196d2fc823

target/board/mainline_arm64/BoardConfig.mk

@@ -26,6 +26,11 @@ TARGET_2ND_CPU_VARIANT := generic
 
 include build/make/target/board/BoardConfigMainlineCommon.mk
 
+# TODO(b/143732851): Remove this after replacing /persit with
+# /mnt/vendor/persist
+BOARD_ROOT_EXTRA_SYMLINKS += /mnt/vendor/persist:/persist
+BOARD_SEPOLICY_DIRS += build/make/target/board/mainline_arm64/sepolicy
+
 TARGET_NO_KERNEL := true
 
 # Build generic A/B format system-only OTA.

target/board/mainline_arm64/sepolicy/OWNERS

@@ -0,0 +1,8 @@
+alanstokes@google.com
+bowgotsai@google.com
+jbires@google.com
+jeffv@google.com
+jgalenson@google.com
+sspatil@google.com
+tomcherry@google.com
+trong@google.com

target/board/mainline_arm64/sepolicy/file.te

@@ -0,0 +1,3 @@
+# TODO(b/143732851): remove this file when the mainline system image
+# no longer need these SoC specific directory
+type persist_file, file_type;

target/board/mainline_arm64/sepolicy/file_contexts

@@ -0,0 +1,5 @@
+# TODO(b/143732851): remove this file when the mainline system image
+# no longer need these SoC specific directory
+
+# /persist
+/persist(/.*)?          u:object_r:persist_file:s0