change extension to custom

src/SPC/builder/extension/zlib.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SPC\builder\extension;
+
+use SPC\builder\Extension;
+use SPC\util\CustomExt;
+
+#[CustomExt('zlib')]
+class zlib extends Extension
+{
+    public function getUnixConfigureArg(): string
+    {
+        return '--with-zlib ZLIB_CFLAGS=-I"' . BUILD_INCLUDE_PATH . '" ' .
+            'ZLIB_LIBS="' . $this->getLibFilesString() . '"';
+    }
+}