title: Missing *.ts files (due to `npm link` ?)
body: <p>I have this import statement in an Angular5 project:</p>
  
  <pre><code>import {plugins, SCECodeGenType} from 'sce-plugins/code-generation';
  </code></pre>
  
  <p>this resolves to this path on my filesystem:</p>
  
  <pre><code>/Users/.../suman-chrome-extension/node_modules/sce-plugins/code-generation/index.d.ts
  </code></pre>
  
  <p>When building the app with <code>ng build -w</code>, I get this error:</p>
  
  <pre><code>ERROR in ../sce-plugins/code-generation/index.ts Module build failed: Error: /Users/alexamil/WebstormProjects/oresoftware/sumanjs/sce-plugins/code-generation/index.ts is missing from the TypeScript compilation. Please make sure it is in your tsconfig via the 'files' or 'include' property.
      at AngularCompilerPlugin.getCompiledFile (/Users/alexamil/WebstormProjects/oresoftware/sumanjs/suman-chrome-extension/node_modules/@ngtools/webpack/src/angular_compiler_plugin.js:662:23)
      at plugin.done.then (/Users/alexamil/WebstormProjects/oresoftware/sumanjs/suman-chrome-extension/node_modules/@ngtools/webpack/src/loader.js:467:39)
      at &lt;anonymous&gt;  @ ./src/app/shared/services/lang.service.ts 14:24-62  @ ./src/app/app.module.ts  @ ./src/main.ts  @ multi ./src/main.ts
  </code></pre>
  
  <p>I believe it's because I am using <code>npm link</code> to link the <code>'sce-plugins'</code> project for local development.</p>
  
  <p>I see some issues with using <code>npm link</code> with Angular5 projects here:</p>
  
  <p><a href="https://github.com/angular/angular-cli/issues/3875" rel="noreferrer">https://github.com/angular/angular-cli/issues/3875</a></p>
  
  <p><a href="https://github.com/angular/angular-cli/issues/8677" rel="noreferrer">https://github.com/angular/angular-cli/issues/8677</a></p>
  
  <p><a href="https://github.com/angular/angular-cli/issues/9376" rel="noreferrer">https://github.com/angular/angular-cli/issues/9376</a></p>
  
  <p>anyone know how to fix?</p>
  
  <p><strong>Update:</strong></p>
  
  <p>It does not seem to have do with <code>npm link</code> perse, or symlinks. If I simply copy the local directory over to <code>node_modules/sce-plugins</code>, I get the same damn error. <em>Yet</em>, if I <code>npm install</code> sce-plugins into node_modules then I do <em>not</em> get the error. Very strange, seems like it has to do with angular-cli, not NPM.</p>