[TIMOB-11669] iOS: Label - postlayout events fired twice for labels.

var win = Ti.UI.createWindow({
    backgroundColor : '#FFF',
    layout : 'vertical'
});
 
var label = Ti.UI.createLabel({
    text : "hello",
    left : 0,
    width : Ti.UI.SIZE,
    height : Ti.UI.SIZE
});
 
label.addEventListener("postlayout", function(e) {
    Ti.API.info("label postlayout");
    //alert("label post layout");
});
 
var doBtn = Ti.UI.createButton({
    title : "do",
    width : Ti.UI.SIZE,
    height : Ti.UI.SIZE
});
 
doBtn.addEventListener("click", function() {
    label.text = "new text";
    label.backgroundColor = '#F00';
    label.left += 20;
 
});
win.add(doBtn);
win.add(label);
win.open();