Add obj tree to EXTRAINCDIR for istep10

Some generated files will be needed by some HWPs in this istep.

Change-Id: Ia8cbb87a4a9dfc5ede40261854df7ce3f22d9d8a
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/89403
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Daniel M Crowell <dcrowell@us.ibm.com>

src/usr/isteps/istep10/makefile

@@ -5,7 +5,7 @@
 #
 # OpenPOWER HostBoot Project
 #
-# Contributors Listed Below - COPYRIGHT 2015,2019
+# Contributors Listed Below - COPYRIGHT 2015,2020
 # [+] International Business Machines Corp.
 #
 #
@@ -51,6 +51,7 @@ EXTRAINCDIR += ${INITFILES_HWP_PATH}
 EXTRAINCDIR += ${PERV_HWP_PATH}
 EXTRAINCDIR += ${OCMB_HWP_PATH}
 EXTRAINCDIR += ${ROOTPATH}/src/import/
+EXTRAINCDIR += ${ROOTPATH}/obj/genfiles/chips/ocmb/explorer/procedures/hwp/memory/lib/
 
 
 OBJS += call_proc_build_smp.o