--- old/make/autoconf/spec.gmk.in	2018-02-05 14:28:52.000000000 -0800
+++ new/make/autoconf/spec.gmk.in	2018-02-05 14:28:52.000000000 -0800
@@ -737,6 +737,8 @@
 USE_EXTERNAL_LIBJPEG:=@USE_EXTERNAL_LIBJPEG@
 USE_EXTERNAL_LIBGIF:=@USE_EXTERNAL_LIBGIF@
 USE_EXTERNAL_LIBZ:=@USE_EXTERNAL_LIBZ@
+LIBZ_CFLAGS:=@LIBZ_CFLAGS@
+LIBZ_LIBS:=@LIBZ_LIBS@
 LIBZIP_CAN_USE_MMAP:=@LIBZIP_CAN_USE_MMAP@
 MSVCR_DLL:=@MSVCR_DLL@
 MSVCP_DLL:=@MSVCP_DLL@