Convert the builder of ios-asan to arm64

Machine assignment is at https://crrev.com/i/7615506

Bug: 361104201
Change-Id: I734f2b7ed2669cad547f7035d4d968c10a54c35d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5800279


Reviewed-by: Lindsay Pasricha <lindsayw@chromium.org>
Commit-Queue: Rahul Kumar Adudodla (xWF) <adudodla@google.com>
Reviewed-by: Ali Juma <ajuma@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1349238}