Disabled parallel builds in Fastfile and changed one of the xarg flags to match upstream

1 job for develop in 8 minutes and 47 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build Only
failed #96904


Name Stage Failure
sanity_build Build Only
* [spaceship] fix typo in `ready_for_beta_submission?` error mes… (#15054) via Steven Sherry

2.127.2 Update mini_magick to prevent vulnerability
* [fastlane] update mini_magick (#15042) via Daniel

To see all new releases, open https://github.com/fastlane/fastlane/releases

Please update using `bundle update fastlane`
ERROR: Job failed: exit status 1