--- old/common/autoconf/spec.gmk.in	2014-02-03 12:18:43.490208094 -0500
+++ new/common/autoconf/spec.gmk.in	2014-02-03 12:18:43.426208208 -0500
@@ -554,6 +554,7 @@
 ENABLE_INTREE_EC=@ENABLE_INTREE_EC@
 USE_EXTERNAL_LIBJPEG:=@USE_EXTERNAL_LIBJPEG@
 USE_EXTERNAL_LIBGIF:=@USE_EXTERNAL_LIBGIF@
+USE_EXTERNAL_LIBPNG:=@USE_EXTERNAL_LIBPNG@
 USE_EXTERNAL_LIBZ:=@USE_EXTERNAL_LIBZ@
 LIBZIP_CAN_USE_MMAP:=@LIBZIP_CAN_USE_MMAP@
 MSVCR_DLL:=@MSVCR_DLL@