@nrwl/workspace/src/generators/library/files/lib/tsconfig.json

{
  "extends": "<%= rootTsConfigPath %>",<% if (js) { %>
  "compilerOptions": {
    "allowJs": true
  },<% } %>
  "files": [],
  "include": [],
  "references": [
    {
      "path": "./tsconfig.lib.json"
    }
  ]
}