xmlto: fix tests

pkgs/tools/typesetting/xmlto/default.nix

···
     sha256 = "0xhj8b2pwp4vhl9y16v3dpxpsakkflfamr191mprzsspg4xdyc0i";
   };
 
-  patchPhase = ''
+  postPatch = ''
+    patchShebangs xmlif/test/run-test
+
     substituteInPlace "xmlto.in" \
       --replace "/bin/bash" "${bash}/bin/bash"
     substituteInPlace "xmlto.in" \