--- old/common/autoconf/spec.gmk.in	2014-02-11 14:07:53.677410097 +0100
+++ new/common/autoconf/spec.gmk.in	2014-02-11 14:07:53.427408655 +0100
@@ -147,9 +147,6 @@
 NASHORN_TOPDIR:=@NASHORN_TOPDIR@
 COPYRIGHT_YEAR:=@COPYRIGHT_YEAR@
 
-# Location where build customization files may be found
-CUSTOM_MAKE_DIR:=@CUSTOM_MAKE_DIR@
-
 # Information gathered from the version.numbers file.
 JDK_MAJOR_VERSION:=@JDK_MAJOR_VERSION@
 JDK_MINOR_VERSION:=@JDK_MINOR_VERSION@
@@ -677,5 +674,14 @@
 JDK_BUNDLE_DIR=$(IMAGES_OUTPUTDIR)/$(JDK_BUNDLE_SUBDIR)
 JRE_BUNDLE_DIR=$(IMAGES_OUTPUTDIR)/$(JRE_BUNDLE_SUBDIR)
 
+# This macro is called to allow inclusion of closed source counterparts.
+# Unless overridden in closed sources, it expands to nothing.
+# Usage: This function is called in an open makefile, with the following 
+# arguments:
+# $1 the name of the repo, or empty if the top-level repo.
+# $2 the name of the makefile
+define IncludeCustomExtension
+endef
+
 # Include the custom-spec.gmk file if it exists
 -include $(dir @SPEC@)/custom-spec.gmk