From eecc4570cd0f775cc83b3ce9c811cd5142e838f2 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Mon, 5 Jul 2021 23:22:44 +0900
Subject: [PATCH] Found library is not usable if the header is not found

---
 ext/zlib/extconf.rb | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ext/zlib/extconf.rb b/ext/zlib/extconf.rb
index 13d0ee2052..d674544f22 100644
--- a/ext/zlib/extconf.rb
+++ b/ext/zlib/extconf.rb
@@ -10,11 +10,12 @@ require 'rbconfig'
 
 dir_config 'zlib'
 
-
+libs = $libs
 if %w'z libz zlib1 zlib zdll zlibwapi'.find {|z| have_library(z, 'deflateReset')} and
     have_header('zlib.h') then
   have_zlib = true
 else
+  $libs = libs
   unless File.directory?(zsrc = "#{$srcdir}/zlib")
     dirs = Dir.open($srcdir) {|z| z.grep(/\Azlib-\d+[.\d]*\z/) {|x|"#{$srcdir}/#{x}"}}
     dirs.delete_if {|x| !File.directory?(x)}