Build error on fresh clone

[msz]

1. Clone repo
2. run yarn

ember build fails with the following error:

TypeError: Path must be a string. Received null
    at assertPath (path.js:28:11)
    at Object.dirname (path.js:1364:5)
    at pathToCaller (/Users/michal/glimmer-test-helpers/node_modules/@glimmer/build/lib/resolve-package.js:17:15)
    at module.exports (/Users/michal/glimmer-test-helpers/node_modules/@glimmer/build/lib/resolve-package.js:8:20)
    at module.exports (/Users/michal/glimmer-test-helpers/node_modules/@glimmer/build/lib/package-dist.js:12:30)
    at Array.map (<anonymous>)
    at module.exports (/Users/michal/glimmer-test-helpers/ember-cli-build.js:8:30)
    at Builder.setupBroccoliBuilder (/Users/michal/glimmer-test-helpers/node_modules/ember-cli/lib/models/builder.js:56:19)
    at new Builder (/Users/michal/glimmer-test-helpers/node_modules/ember-cli/lib/models/builder.js:30:10)
    at BuildTask.run (/Users/michal/glimmer-test-helpers/node_modules/ember-cli/lib/tasks/build.js:15:19)