Remove journaling from read-only FS to save space

The read-only partitions don't need journaling.

Bug: 18430740
Change-Id: I44b88c43a506d8b64f7cf00910136cfe1c524c24
diff --git a/releasetools.py b/releasetools.py
index dba721e..26d9dcc 100644
--- a/releasetools.py
+++ b/releasetools.py
@@ -32,6 +32,10 @@
   else:
     WriteRadio(info, radio_img)
 
+def IncrementalOTA_InstallBegin(info):
+  info.script.Unmount("/system")
+  info.script.TunePartition("/system", "-O", "^has_journal")
+  info.script.Mount("/system")
 
 def IncrementalOTA_InstallEnd(info):
   try: