find internal zlib in nmake buildsystem

--- curl/winbuild/MakefileBuild.vc.orig2	2021-10-27 20:44:48.685237000 +0200
+++ curl/winbuild/MakefileBuild.vc	2021-10-27 20:47:23.792407400 +0200
@@ -244,8 +244,9 @@
 ZLIB_LIB_DIR = $(ZLIB_PATH)\lib
 ZLIB_LFLAGS  = $(ZLIB_LFLAGS) "/LIBPATH:$(ZLIB_LIB_DIR)"
 !ELSE
-ZLIB_INC_DIR = $(DEVEL_INCLUDE)
-ZLIB_LIB_DIR = $(DEVEL_LIB)
+ZLIB_INC_DIR = $(WORKDIR)/UnpackedTarball/zlib
+ZLIB_LIB_DIR = $(WORKDIR)/LinkTarget/StaticLibrary
+ZLIB_LFLAGS  = $(ZLIB_LFLAGS) "/LIBPATH:$(ZLIB_LIB_DIR)"
 !ENDIF
 
 # Depending on how zlib is built the libraries have different names, we
