Follow up on @angular-devkit/build-angular spec_large error

This should really be using Ivy but was getting the error below on every second build.
`ERROR in Cannot read property 'incrementalState' of null`

See https://github.com/angular/angular-cli/pull/15847/commits/0a4dd9b209cbaaaabbe25bc09cb538948fa4b148