Also, copy ios_arm64 to ios_arm64_dbg, so we can rename the bot.
Bug: chromium:774381
No-Try: true
Change-Id: I38a447e229ded6874a661bb6f39ae8ebfdcb194d
Reviewed-on: https://webrtc-review.googlesource.com/22580
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20665}