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/rootdir/init.rc b/rootdir/init.rc
index fb64736..12c46eb 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -92,6 +92,12 @@
     # checker programs.
     mkdir /dev/fscklogs 0770 root system
 
+    # Create tmpfs for use by the shell user.
+    mount tmpfs tmpfs /tmp
+    restorecon /tmp
+    chown shell shell /tmp
+    chmod 0771 /tmp
+
 on init
     sysclktz 0