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

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

private/preloads_copy.te

+type preloads_copy, domain, coredomain;
+type preloads_copy_exec, system_file_type, exec_type, file_type;
+
+init_daemon_domain(preloads_copy)
+
+allow preloads_copy shell_exec:file rx_file_perms;
+allow preloads_copy toolbox_exec:file rx_file_perms;
+allow preloads_copy preloads_data_file:dir create_dir_perms;
+allow preloads_copy preloads_data_file:file create_file_perms;
+allow preloads_copy preloads_media_file:dir create_dir_perms;
+allow preloads_copy preloads_media_file:file create_file_perms;
+
+# Allow to copy from /postinstall
+allow preloads_copy system_file:dir r_dir_perms;