title: Error while running ng server about Require Stack - Angular 9
body: <p>When i run ng serve --open in my project it shows</p>
  
  <pre><code>An unhandled exception occurred: Cannot find module '@angular-devkit/build-angular/package.json'
  Require stack:
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@angular-devkit\architect\node\node-modules-architect-host.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@angular-devkit\architect\node\index.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\models\architect-command.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\commands\serve-impl.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@angular-devkit\schematics\tools\export-ref.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@angular-devkit\schematics\tools\index.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\utilities\json-schema.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\models\command-runner.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\lib\cli\index.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\lib\init.js
  - C:\Users\Alexander\AppData\Roaming\npm\node_modules\@angular\cli\bin\ng
  See "C:\Users\ALEXAN~1\AppData\Local\Temp\ng-mrsQtL\angular-errors.log" for further details.
  </code></pre>
  
  <p>this is my ng --version:</p>
  
  <pre><code>Angular CLI: 9.1.0
  Node: 12.15.0
  OS: win32 x64
  
  Angular: 9.1.0
  ... animations, common, compiler, core, forms, platform-browser
  ... platform-browser-dynamic, router
  Ivy Workspace: Yes
  
  Package                         Version
  ---------------------------------------------------------
  @angular-devkit/architect       0.901.0 (cli-only)
  @angular-devkit/build-angular   &lt;error&gt;
  @angular-devkit/core            9.1.0 (cli-only)
  @angular-devkit/schematics      9.1.0 (cli-only)
  @angular/cli                    &lt;error&gt;
  @angular/compiler-cli           &lt;error&gt;
  @angular/language-service       &lt;error&gt;
  @schematics/angular             9.1.0 (cli-only)
  @schematics/update              0.901.0 (cli-only)
  rxjs                            6.5.4
  typescript                      &lt;error&gt;
  </code></pre>
  
  <p>I think the problem is with my npm install -g @angular/cli.
  it doesnt download dev dependencies of angular</p>
  
  <p>Pls, i tried to fix for days</p>