fix libxml2 links

packages/l/libxml2/xmake.lua

@@ -13,7 +13,14 @@ package("libxml2")
     end
 
     add_includedirs("include/libxml2")
-    add_links("xml2")
+
+    on_load(function (package)
+        if package:plat() == "windows" then
+            package:add("links", "libxml2_a")
+        else
+            package:add("links", "xml2")
+        end
+    end)
 
     if is_plat("windows") and winos.version():gt("winxp") then
         on_install("windows", function (package)