mac-arm64: Update toolchain to Xcode 12.2rc (12B5044c)

This version of Xcode updates the macOS SDK to 11.0 20A5408a (closer to
11.0 than 11.0.1).

CQ-Include-Trybots: luci.chromium.try:mac-arm64-rel
Change-Id: I0bcfc826f5b64d90da8f33a9f840b3c962bce099
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2522003
Auto-Submit: 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@{#824699}

build/mac_toolchain.py

@@ -34,9 +34,9 @@ MAC_BINARIES_TAG = {
     # This contains binaries from Xcode 12.1, along with the 10.15 SDK (aka
     # 12A7403).
     'default': '77fpfpUrA6kBF3yEaMBEvWHOomBWqoiRT3bEJ4bXxvUC',
-    # This contains binaries from Xcode 12.2 beta 3, along with the
-    # 11 SDK (aka 12B5035g).
-    'xcode_12_beta': 'Hbv2yK-6odRW8p2nfq7EZyaOWRpcEiMn5mvZpG9exTwC',
+    # This contains binaries from the Xcode 12.2 release candidate, along with
+    # the macOS 11 SDK (aka 12B5044c).
+    'xcode_12_beta': 'UwKVijd1FvMzmCAjyoYq_sw6xXJZpw_mGBH420gwlrwC',
 }
 
 # The toolchain will not be downloaded if the minimum OS version is not met.