[dart_ci] Special case CIPD package name for arm64

Change-Id: Id1a7a3f11dcf5f4693663074dbbc331e21d8e8cb
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/203881
Reviewed-by: Alexander Thomas <athom@google.com>
Commit-Queue: Karl Klose <karlklose@google.com>
2 files changed