title: stylePreprocessorOptions for libraries, where should I put in in angular.json?
body: <p>I'm trying to use <code>stylePreprocessorOptions</code> in order to include a path to my variables folders <strong>for a library project</strong> like so :</p>
  
  <pre><code>"stylePreprocessorOptions": {
    "includePaths": [
      "styles/variables"
    ]
  }
  </code></pre>
  
  <p>Then I use <code>@import 'colors';</code> within the scss file. But it doesnt work while doing <code>ng serve</code> :</p>
  
  <pre><code>@import 'colors';
         ^
        Can't find stylesheet to import.
  </code></pre>
  
  <p>Here is the full library in angular.json :</p>
  
  <pre><code>        "ui-table": {
              "root": "libs/ui/table",
              "sourceRoot": "libs/ui/table/src",
              "projectType": "library",
              "prefix": "xxx",
              "architect": {
                  "build": {
                      "builder": "@angular-devkit/build-ng-packagr:build",
                      "options": {
                          "tsConfig": "libs/ui/table/tsconfig.lib.json",
                          "project": "libs/ui/table/ng-package.json",
                          "stylePreprocessorOptions": {
                              "includePaths": [
                                  "styles/variables"
                              ]
                          }
                      }
                  },
                  "lint": {
                      "builder": "@angular-devkit/build-angular:tslint",
                      "options": {
                          "tsConfig": ["libs/ui/table/tsconfig.lib.json"],
                          "exclude": ["**/node_modules/**"]
                      }
                  }
              },
              "schematics": {
                  "@nrwl/schematics:component": {
                      "styleext": "scss"
                  }
              }
          },
  
  </code></pre>
  
  <p>How can I use <code>stylePreprocessorOptions</code> in a library in Angular?</p>
  
  <p>Thanks!</p>