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

rootdir/Android.mk

@@ -97,7 +97,7 @@ endif
 # create some directories (some are mount points) and symlinks
 LOCAL_POST_INSTALL_CMD := mkdir -p $(addprefix $(TARGET_ROOT_OUT)/, \
     dev proc sys system data data_mirror odm oem acct config storage mnt apex bootstrap-apex debug_ramdisk \
-    linkerconfig second_stage_resources postinstall $(BOARD_ROOT_EXTRA_FOLDERS)); \
+    linkerconfig second_stage_resources postinstall tmp $(BOARD_ROOT_EXTRA_FOLDERS)); \
     ln -sf /system/bin $(TARGET_ROOT_OUT)/bin; \
     ln -sf /system/etc $(TARGET_ROOT_OUT)/etc; \
     ln -sf /data/user_de/0/com.android.shell/files/bugreports $(TARGET_ROOT_OUT)/bugreports; \

rootdir/init.rc

@@ -92,6 +92,12 @@ on early-init
     # 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