Angular directive how to add an attribute to the element?

I'm wondering what's the way to do work this snippet:

//html
<div ng-app="app">
    <div ng-controller="AppCtrl">
        <a my-dir ng-repeat="user in users">{{user.name}}</a>
    </div>
</div>

//js
var app = angular.module('app', []);
app.controller("AppCtrl", function ($scope) {
    $scope.users = [{name:'John',id:1},{name:'anonymous'}];
    $scope.fxn = function() {
        alert('It works');
    };

})  
app.directive("myDir", function ($compile) {
    return {
        link:function(scope,el){
            el.attr('ng-click','fxn()');
            //$compile(el)(scope); with this the script go mad 
        }
     };
});

I know it's about the compile phase but I don't get the point so a short explanation would be very appreciate.

A directive which adds another directive to the same element:

Similar answers:

• How to get ng-class with $dirty working in a directive?
• creating a new directive with angularjs

Here is a plunker: http://plnkr.co/edit/ziU8d826WF6SwQllHHQq?p=preview

app.directive("myDir", function($compile) {
  return {
    priority:1001, // compiles first
    terminal:true, // prevent lower priority directives to compile after it
    compile: function(el) {
      el.removeAttr('my-dir'); // necessary to avoid infinite compile loop
      el.attr('ng-click', 'fxn()');
      var fn = $compile(el);
      return function(scope){
        fn(scope);
      };
    }
  };
});

Much cleaner solution - not to use ngClick at all:

A plunker: http://plnkr.co/edit/jY10enUVm31BwvLkDIAO?p=preview

app.directive("myDir", function($parse) {
  return {
    compile: function(tElm,tAttrs){
      var exp = $parse('fxn()');
      return function (scope,elm){
        elm.bind('click',function(){
          exp(scope);
        });  
      };
    }
  };
});

You can try this:

<div ng-app="app">
    <div ng-controller="AppCtrl">
        <a my-dir ng-repeat="user in users" ng-click="fxn()">{{user.name}}</a>
    </div>
</div>

<script>
var app = angular.module('app', []);

function AppCtrl($scope) {
        $scope.users = [{ name: 'John', id: 1 }, { name: 'anonymous' }];
        $scope.fxn = function () {
            alert('It works');
        };
    }

app.directive("myDir", function ($compile) {
    return {
        scope: {ngClick: '='}
    };
});
</script>