make sure es6 will compile correctly

Tools/Gulp/config.json

@@ -999,9 +999,12 @@
         },
         "debug": {
             "files": [
-                "../../src/Debug/babylon.debugModules.js",
+                "../../src/Debug/babylon.skeletonViewer.js",
+                "../../src/Debug/babylon.axesViewer.js",
+                "../../src/Debug/babylon.boneAxesViewer.js",
                 "../../src/Debug/babylon.rayHelper.js",
                 "../../src/Debug/babylon.debugLayer.js",
+                "../../src/Debug/babylon.physicsViewer.js",
                 "../../src/Rendering/babylon.boundingBoxRenderer.js"
             ],
             "dependUpon": [

Tools/Gulp/gulp-addES6Exports.js

@@ -37,7 +37,7 @@ globalObject["${base}"] = ${base}${(subModule && !extendsRoot) ? '.' + varName :
             let enumMatcher = new RegExp(`\\(${base}\\.([A-Za-z0-9].*)= {}\\)`, "g");
             let enumMatch = enumMatcher.exec(fileContent);
             while (enumMatch != null) {
-                if (enumMatch[1]) {
+                if (enumMatch[1] && listOfExports.indexOf(enumMatch[1]) === -1) {
                     listOfExports.push(enumMatch[1]);
                 }
                 enumMatch = enumMatcher.exec(fileContent);