It says yarn is not installed when it's installed

### What version of Turborepo are you using?

1.0.10

### Describe the Bug

It says yarn is not installed but it is installed

![Screen Shot 2021-12-15 at 1 06 18](https://user-images.githubusercontent.com/11366687/146139852-d9f46b55-1673-4b55-a6a3-aeee87af9596.png)




### Expected Behavior

I can use yarn

### To Reproduce

run `npx create-turbo@latest`

