Bolt install returning 0 error code when yarn install fails

Just happened in CI twice now where network connectivity issues caused yarn to fail, but bolt install didnt return a non-zero code.

Will look into this

| Title | Description
| --------------------|------------
| Version | 0.20.7

Start at the bolt install entry point and inspect how the yarn install result is handled. Reproduce the reported CI failure or simulate a failed yarn install; done means bolt install returns a non-zero exit code when yarn install fails.

Written by the indexing model from the issue text.