mac: Update toolchain to Xcode 12.2 (12B45b)

This version of Xcode updates the macOS SDK to 11.0 20A2408 (closer to
11.0 than 11.0.1).

Bug: 1108831
Change-Id: I9fe09af1d325e0e68e7351fe7f92ce84e676c922
CQ-Include-Trybots: luci.chromium.try:mac-arm64-rel
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2537573
Commit-Queue: Mark Mentovai <mark@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827292}

build/mac_toolchain.py

@@ -29,11 +29,10 @@ import shutil
 import subprocess
 import sys
 
-# This contains binaries from the Xcode 12.2 release candidate, along with the
-# macOS 11 SDK (aka 12B5044c). To build these packages, see comments in
-# build/xcode_binaries.yaml
+# This contains binaries from Xcode 12.2 12B45b, along with the macOS 11 SDK.
+# To build these packages, see comments in build/xcode_binaries.yaml
 MAC_BINARIES_LABEL = 'infra_internal/ios/xcode/xcode_binaries/mac-amd64'
-MAC_BINARIES_TAG = 'UwKVijd1FvMzmCAjyoYq_sw6xXJZpw_mGBH420gwlrwC'
+MAC_BINARIES_TAG = 'Uez8drOxhQfCBsViLtHwcbwmi3VzShwUKE_WyBI4lzEC'
 
 # The toolchain will not be downloaded if the minimum OS version is not met. 19
 # is the major version number for macOS 10.15. 12B5044c (Xcode 12.2rc) only runs

docs/mac_arm64.md

@@ -15,11 +15,10 @@ that continuously runs tests. Most tests pass.
 You can build Chrome for arm macs on an Intel Mac. To build for arm64, you have
 to do 2 things:
 
-1. use the `MacOSX11.0.sdk` that comes with the
-   Xcode 12.2 release candidate. If you're on Google's corporate network, this
-   SDK is part of the hermetic toolchain and will be used automatically.
-   Otherwise, manually download and install this version of Xcode and make it
-   the active Xcode with `xcode-select`.
+1. use the `MacOSX11.0.sdk` that comes with Xcode 12.2. If you're on Google's
+   corporate network, this SDK is part of the hermetic toolchain and will be
+   used automatically. Otherwise, manually download and install this version of
+   Xcode and, if necessary, make it the active Xcode with `xcode-select`.
 
 2. Add `target_cpu = "arm64"` to your `args.gn`.