エラー

（以下全文）

Schema validation failed with the following errors:
  Data path ".builders['app-shell']" should have required property 'class'.
Error: Schema validation failed with the following errors:
  Data path ".builders['app-shell']" should have required property 'class'.
    at MergeMapSubscriber.project (/Users/uparupa/hogre/node_modules/@angular/cli/node_modules/@angular-devkit/core/src/workspace/workspace.js:173:42)
    at MergeMapSubscriber._tryNext (/Users/uparupa/hoge/node_modules/rxjs/internal/operators/mergeMap.js:69:27)
    at MergeMapSubscriber._next (/Users/uparupa/hoge/node_modules/rxjs/internal/operators/mergeMap.js:59:18)
    at MergeMapSubscriber.Subscriber.next (/Users/uparupa/hoge/node_modules/rxjs/internal/Subscriber.js:66:18)
    at MergeMapSubscriber.notifyNext (/Users/uparupa/hoge/node_modules/rxjs/internal/operators/mergeMap.js:92:26)
    at InnerSubscriber._next (/Users/uparupa/hoge/node_modules/rxjs/internal/InnerSubscriber.js:28:21)
    at InnerSubscriber.Subscriber.next (/Users/uparupa/hoge/node_modules/rxjs/internal/Subscriber.js:66:18)
    at MapSubscriber._next (/Users/uparupa/hoge/node_modules/rxjs/internal/operators/map.js:55:26)
    at MapSubscriber.Subscriber.next (/Users/uparupa/hoge/node_modules/rxjs/internal/Subscriber.js:66:18)
    at SwitchMapSubscriber.notifyNext (/Users/uparupa/hoge/node_modules/rxjs/internal/operators/switchMap.js:86:26)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! hoge@0.0.0 start: `ng serve`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the osarchive@0.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

解決

angular.jsonのbuilderを下記に変更

angular.json

"@angular-devkit/build-angular": "^0.10.0",

その後

$ npm install
$ ng update @angular/cli @angular/core
$ npm audit fix

を実行すると僕の環境では直りました...ご参考までに...