Update backing build

Change-Id: Id777f55dd447439d8f4c5b7afaf2a586cbc2463a
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/55406
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Reviewed-by: Sachin Gupta <sgupta2m@in.ibm.com>

customrc

@@ -33,6 +33,6 @@ export SANDBOXNAME=test_sb
 #export WORKSPACE=<set it to your root ppe directory. This is required if you
 #                  to use build script locally>
 export MACHINE=NIMBUS
-export BACKING_BUILD=/esw/fips911/Builds/b0109a_1802.911/
+export BACKING_BUILD=/esw/fips911/Builds/b0309a_1812.911/
 export SIMICSOPTIONS="-nre"