Add support for Xcode 12.4 (12D4e) (#35739)

Author: benrimmington

utils/build-script

@@ -57,6 +57,7 @@ _SUPPORTED_XCODE_BUILDS = [
     ("12.2 Release Candidate", "12B5044c"),
     ("12.2", "12B45b"),
     ("12.3", "12C33"),
+    ("12.4", "12D4e"),
 ]
 
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