title: angular-devkit/build-angular version 0.13.4 - configuration.output has an unknown property 'futureEmitAssets'
body: <p>I just upgraded a project from angular-devkit/build-angular v0.11.4 to v0.13.4. I now receive the following error:</p>
  
  <pre><code>Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
   - configuration.output has an unknown property 'futureEmitAssets'. 
  These properties are valid:
     object { auxiliaryComment?, chunkCallbackName?, chunkFilename?, chunkLoadTimeout?, crossOriginLoading?, devtoolFallbackModuleFilenameTemplate?, devtoolLineToLine?, devtoolModuleFilenameTemplate?, devtoolNamespace?, filename?, globalObject?, hashDigest?, hashDigestLength?, hashFunction?, hashSalt?, hotUpdateChunkFilename?, hotUpdateFunction?, hotUpdateMainFilename?, jsonpFunction?, jsonpScriptType?, library?, libraryExport?, libraryTarget?, path?, pathinfo?, publicPath?, sourceMapFilename?, sourcePrefix?, strictModuleExceptionHandling?, umdNamedDefine?, webassemblyModuleFilename? }
     -&gt; Options affecting the output of the compilation. `output` options tell webpack how to write the compiled files to disk.
  WebpackOptionsValidationError: Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
   - configuration.output has an unknown property 'futureEmitAssets'. These properties are valid:
     object { auxiliaryComment?, chunkCallbackName?, chunkFilename?, chunkLoadTimeout?, crossOriginLoading?, devtoolFallbackModuleFilenameTemplate?, devtoolLineToLine?, devtoolModuleFilenameTemplate?, devtoolNamespace?, filename?, globalObject?, hashDigest?, hashDigestLength?, hashFunction?, hashSalt?, hotUpdateChunkFilename?, hotUpdateFunction?, hotUpdateMainFilename?, jsonpFunction?, jsonpScriptType?, library?, libraryExport?, libraryTarget?, path?, pathinfo?, publicPath?, sourceMapFilename?, sourcePrefix?, strictModuleExceptionHandling?, umdNamedDefine?, webassemblyModuleFilename? }
     -&gt; Options affecting the output of the compilation. `output` options tell webpack how to write the compiled files to disk.```
  </code></pre>
  
  <p>My <code>angular.json</code></p>
  
  <pre><code>{
    "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
    "version": 1,
    "newProjectRoot": "projects",
    "projects": {
      "ui": {
        "root": "",
        "sourceRoot": "src",
        "projectType": "application",
        "prefix": "app",
        "schematics": {},
        "architect": {
          "build": {
            "builder": "@angular-devkit/build-angular:browser",
            "options": {
              "outputPath": "dist",
              "index": "src/index.html",
              "main": "src/main.ts",
              "polyfills": "src/polyfills.ts",
              "tsConfig": "src/tsconfig.app.json",
              "assets": [
                "src/favicon.ico",
                "src/assets"
              ],
              "styles": [
                "bootstrap/css/bootstrap.min.css",
                "node_modules/font-awesome/css/font-awesome.css",
                "node_modules/startbootstrap-simple-sidebar/css/simple-sidebar.css",
                "node_modules/chart.js/dist/Chart.min.js",
                "src/styles.css"
              ],
              "scripts": [
                "node_modules/jquery/dist/jquery.min.js",
                "bootstrap/js/bootstrap.min.js"
              ]
            },
            "configurations": {
              "production": {
                "fileReplacements": [
                  {
                    "replace": "src/environments/environment.ts",
                    "with": "src/environments/environment.prod.ts"
                  }
                ],
                "optimization": true,
                "outputHashing": "all",
                "sourceMap": false,
                "extractCss": true,
                "namedChunks": false,
                "aot": true,
                "extractLicenses": true,
                "vendorChunk": false,
                "buildOptimizer": true,
                "budgets": [
                  {
                    "type": "initial",
                    "maximumWarning": "3mb",
                    "maximumError": "5mb"
                  }
                ]
              }
            }
          },
          "serve": {
            "builder": "@angular-devkit/build-angular:dev-server",
            "options": {
              "browserTarget": "ui:build"
            },
            "configurations": {
              "production": {
                "browserTarget": "ui:build:production"
              }
            }
          },
          "extract-i18n": {
            "builder": "@angular-devkit/build-angular:extract-i18n",
            "options": {
              "browserTarget": "ui:build"
            }
          },
          "test": {
            "builder": "@angular-devkit/build-angular:karma",
            "options": {
              "main": "src/test.ts",
              "karmaConfig": "./karma.conf.js",
              "polyfills": "src/polyfills.ts",
              "tsConfig": "src/tsconfig.spec.json",
              "scripts": [
                "node_modules/jquery/dist/jquery.min.js",
                "bootstrap/js/bootstrap.min.js"
              ],
              "styles": [
                "bootstrap/css/bootstrap.min.css",
                "node_modules/font-awesome/css/font-awesome.css",
                "node_modules/startbootstrap-simple-sidebar/css/simple-sidebar.css",
                "node_modules/chart.js/dist/Chart.min.js",
                "src/styles.css"
              ],
              "assets": [
                "src/favicon.ico",
                "src/assets"
              ]
            }
          },
          "lint": {
            "builder": "@angular-devkit/build-angular:tslint",
            "options": {
              "tsConfig": [
                "src/tsconfig.app.json",
                "src/tsconfig.spec.json"
              ],
              "exclude": [
                "**/node_modules/**"
              ]
            }
          }
        }
      },
      "ui-e2e": {
        "root": "",
        "sourceRoot": "",
        "projectType": "application",
        "architect": {
          "e2e": {
            "builder": "@angular-devkit/build-angular:protractor",
            "options": {
              "protractorConfig": "./protractor.conf.js",
              "devServerTarget": "ui:serve"
            }
          },
          "lint": {
            "builder": "@angular-devkit/build-angular:tslint",
            "options": {
              "tsConfig": "e2e/tsconfig.e2e.json",
              "exclude": [
                "**/node_modules/**"
              ]
            }
          }
        }
      }
    },
    "defaultProject": "ui"
  }
  </code></pre>
  
  <p>My startup command is <code>ng serve --proxy-config proxy.config.js</code></p>
  
  <p>I cannot find any instance of <code>futureEmitAssets</code> in my code. Anyone have any ideas?</p>