Angular编译器gendir选项不起作用

Question

所以我有这个npm脚本

"scripts": {
    ...
    "aot": "./node_modules/.bin/ngc -p tsconfig.json"
}

在tsconfig.json中，我拥有

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "lib": [ "dom", "esnext" ],
    "target" : "ES2018",
    "baseUrl": "./src",
    "moduleResolution": "node",
    "module": "commonjs",
    "sourceMap": true,
    "inlineSources": true
  },
  "angularCompilerOptions": {
    "genDir": "./ngfactories",
    "skipMetadataEmit" : true
  }
}

我使用的软件包

"devDependencies": {
    "@angular/compiler-cli": "^6.1.9",
    "typescript": "^2.9.2",
    "@ngtools/webpack": "^6.2.2",
    ...
  },
  dependencies: {
    "@angular/compiler": "^6.1.9",
    ...
  } 

问题是，运行npm run aot不会在genDir指定的./ngfactories目录中生成.ngfactory.js文件等。而是将它们与原始.ts文件一起生成。我在做什么错，如何使angular编译器在适当的./ngfactories目录中生成ngfactor？