*Don't* configure zlib so we get the generic zconf.h

code/zlib-1.3.1/zconf.h

@@ -433,11 +433,11 @@ typedef uLong FAR uLongf;
    typedef unsigned long z_crc_t;
 #endif
 
-#if 1    /* was set to #if 1 by ./configure */
+#ifdef HAVE_UNISTD_H    /* may be set to #if 1 by ./configure */
 #  define Z_HAVE_UNISTD_H
 #endif
 
-#if 1    /* was set to #if 1 by ./configure */
+#ifdef HAVE_STDARG_H    /* may be set to #if 1 by ./configure */
 #  define Z_HAVE_STDARG_H
 #endif