mac: Update Xcode hermetic package binaries to include atos

New packages are provided for both Xcode 11.2.1 11B53 and 12b4 12A8179i,
identical to the old packages with the inclusion of atos after
955c73fb.

Bug: 1113466
Change-Id: If8c18cc0881526d006cad35a6f45f2aa2af2d611
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2360324
Commit-Queue: Mark Mentovai <mark@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Auto-Submit: Mark Mentovai <mark@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798857}

build/mac_toolchain.py

@@ -33,10 +33,10 @@ MAC_BINARIES_LABEL = 'infra_internal/ios/xcode/xcode_binaries/mac-amd64'
 MAC_BINARIES_TAG = {
     # This contains binaries from Xcode 11.2.1, along with the 10.15 SDKs (aka
     # 11B53).
-    'default': 'X5ZbqG_UKa-N64_XSBkAwShWPtzskeXhQRfpzc_1KUYC',
+    'default': 'wXywrnOhzFxwLYlwO62UzRxVCjnu6DoSI2D2jrCd00gC',
     # This contains binaries from Xcode 12 beta 4, along with the
     # 11 SDK (aka 12A8179i).
-    'xcode_12_beta': 'LGFg5-BnRNuEMwcDjlvByCaT4S3O_nGfUOsj18xeXJIC',
+    'xcode_12_beta': 'cDHYuQ9HUo7nJd1w8GfZfifcjGt2ZWVNykJn399Xz6YC',
 }
 
 # The toolchain will not be downloaded if the minimum OS version is not met.