Improve robustness of iOS CircleCI Pipelines (facebook#36419)

Summary:
Pull Request resolved: facebook#36419

After migrating to Xcode 14.2.0, some contributors were receiving CircleCI Machines that were not able to install Ruby 3.2.0.

This change should improve the robustness of the pipelines, ensuring that `ruby-build` can always find the version of Ruby it needs

## Changelog:
[internal] - Make sure CircleCI always find the right version of Ruby

Reviewed By: cortinico

Differential Revision: D43944878

fbshipit-source-id: 89d9fcc6ae346003e96c2a8f4103a83a7d2f3204

.circleci/config.yml

@@ -192,6 +192,10 @@ commands:
 
  # Install the right version of ruby
  if [[ -z "$(rbenv versions | grep << parameters.ruby_version >>)" ]]; then
+ # ensure that `ruby-build` can see all the available versions of Ruby
+ # some PRs received machines in a weird state, this should make the pipelines
+ # more robust.
+ brew update && brew upgrade ruby-build
  rbenv install << parameters.ruby_version >>
  fi