title: ng build --prod is not generating vendor.bundle.js
body: <p>I am using node version 8.9.4,
  npm version 5.6.0 I have no clue why this is happening the
  <code>ng build --dev</code> is generating vendor.bundle.js while <code>ng build --prod</code> is not generating vendor.bundle.js here is the screenshot<br></p>
  
  <p><strong>output with ng build--prod</strong>
  [<img src="https://i.stack.imgur.com/GMxkX.png" alt="enter image description here"><br>
  <strong>[output with ng-build --dev]</strong> 
     <a href="https://i.stack.imgur.com/Ev5HV.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Ev5HV.png" alt="enter image description here"></a></p>
  
  <p>Here is my package.json</p>
  
  <pre><code>`{
    "name": "app1",
    "version": "0.0.0",
    "license": "MIT",
    "scripts": {
      "ng": "ng",
      "start": "ng serve",
      "build": "ng build --prod",
      "test": "ng test",
      "lint": "ng lint",
      "e2e": "ng e2e"
    },
    "private": true,
    "dependencies": {
      "@angular-devkit/core": "0.0.28",
      "@angular/animations": "^5.0.0",
      "@angular/common": "^5.0.0",
      "@angular/compiler": "^5.0.0",
      "@angular/core": "^5.0.0",
      "@angular/forms": "^5.0.0",
      "@angular/http": "^5.0.0",
      "@angular/platform-browser": "^5.0.0",
      "@angular/platform-browser-dynamic": "^5.0.0",
      "@angular/router": "^5.0.0",
      "core-js": "^2.4.1",
      "rxjs": "^5.5.2",
      "zone.js": "^0.8.14"
    },
    "devDependencies": {
      "@angular/cli": "1.6.3",
      "@angular/compiler-cli": "^5.0.0",
      "@angular/language-service": "^5.0.0",
      "@types/jasmine": "~2.5.53",
      "@types/jasminewd2": "~2.0.2",
      "@types/node": "~6.0.60",
      "codelyzer": "^4.0.1",
      "jasmine-core": "~2.6.2",
      "jasmine-spec-reporter": "~4.1.0",
      "karma": "~1.7.0",
      "karma-chrome-launcher": "~2.1.1",
      "karma-cli": "~1.0.1",
      "karma-coverage-istanbul-reporter": "^1.2.1",
      "karma-jasmine": "~1.1.0",
      "karma-jasmine-html-reporter": "^0.2.2",
      "protractor": "~5.1.2",
      "ts-node": "~3.2.0",
      "tslint": "~5.7.0",
      "typescript": "~2.4.2"
    }
  }
  </code></pre>
  
  <p>`</p>