Add sepolicy for preloads_copy script

Copied from device/google/crosshatch-sepolicy.

Test: diff files in system/etc/selinux before and after for aosp_marlin
Change-Id: I518c43af9c217483bdab02424e4aef0270aad366
diff --git a/private/file_contexts b/private/file_contexts
index b361ccd..ee295ca 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -270,6 +270,7 @@
 /system/bin/logwrapper  u:object_r:system_file:s0
 /system/bin/vdc         u:object_r:vdc_exec:s0
 /system/bin/cppreopts.sh   u:object_r:cppreopts_exec:s0
+/system/bin/preloads_copy.sh u:object_r:preloads_copy_exec:s0
 /system/bin/preopt2cachename u:object_r:preopt2cachename_exec:s0
 /system/bin/install-recovery.sh u:object_r:install_recovery_exec:s0
 /system/bin/dex2oat(d)?     u:object_r:dex2oat_exec:s0