Really fix zlib build with GCC 4.
Note: mandatory check (NEED_CHECK) was skipped
@@ -433,15 +433,19 @@ typedef uLong FAR uLongf;
#ifdef __GNUC__
# define Z_HAVE_UNISTD_H
-#elif __has_include(<unistd.h>)
+#else
+# if __has_include(<unistd.h>)
# define Z_HAVE_UNISTD_H
# endif
+#endif
#ifdef __GNUC__
# define Z_HAVE_UNISTD_H
-#elif __has_include(<stdarg.h>)
+#else
+# if __has_include(<stdarg.h>)
# define Z_HAVE_STDARG_H
# endif
+#endif
#ifdef STDC
# ifndef Z_SOLO
