xmlstarlet: fix build (#412407)

pkgs/by-name/xm/xmlstarlet/package.nix

···
       url = "https://sourceforge.net/p/xmlstar/patches/_discuss/thread/890e29655a/66ca/attachment/0001-Fix-build-with-libxml2-2.12.patch";
       hash = "sha256-XEk7aFOdrzdec1j2ffERJQbLH0AUNJA52QwA9jf4XWA=";
     })
+    (fetchurl {
+      name = "libxml-2.14.patch";
+      url = "https://github.com/termux/termux-packages/raw/39135f3f1190268d127b998c2c6040d9af611ba5/packages/xmlstarlet/libxml2-2.14-attribute-unused.patch";
+      hash = "sha256-zHkUQsrhPLWI3kdfCITbcixpBmDRmxSM2Viz5R+8q5E=";
+    })
   ];
 
   preConfigure = ''