In #39470, the `deploy-to-firebase.sh` script (used to deploy AIO to Firebase when building an upstream branch), was replaced by an equivalent JS script. In this new `deploy-to-firebase.js` script, we were overly aggressive with suppressing command output, which made it hard to investigate failures ([example failing CI job][1]). This commit updates the `deploy-to-firebase.js` script to capture command output as usual in the CI job logs. This makes the output similar to the one generated by the old [deploy-to-firebase.sh][2] script ([example CI logs][3]). One concern with capturing command output is having the value of a secret environment variables leaked in the logs. This is not the case here, since: 1. The secret env vars are not printed from the commands that use them. 2. CircleCI will [mask the values of secret env vars][4] in the output. As an extra precaution (although not strictly necessary), we run `yarn` with the `--silent` option, which avoid echoing the executed yarn commands. [1]: https://circleci.com/gh/angular/angular/849310 [2]: https://github.com/angular/angular/blob/3b0b7d22109c79b4dceb/aio/scripts/deploy-to-firebase.sh [3]: https://circleci.com/gh/angular/angular/848109 [4]: https://circleci.com/docs/2.0/env-vars/#secrets-masking PR Close #39596