Mount /tmp as tmpfs.

/tmp is a volatile temporary storage location for the shell user.
As with /data/local/tmp, it is owned by shell:shell and is chmod 771.

Bug: 311263616
Change-Id: Ice0229d937989b097971d9db434d5589ac2da99a
diff --git a/private/file_contexts b/private/file_contexts
index 1fdeb14..a1bc85f 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -54,6 +54,7 @@
 /sys                u:object_r:sysfs:s0
 /apex               u:object_r:apex_mnt_dir:s0
 /bootstrap-apex     u:object_r:apex_mnt_dir:s0
+/tmp                u:object_r:shell_data_file:s0
 
 # Postinstall directories
 /postinstall         u:object_r:postinstall_mnt_dir:s0