Switching macOS builds to the macOS 11 SDK and Xcode 12.2

[Mark Mentovai]

Welcome to the future!

https://chromium-review.googlesource.com/c/2530914, which landed this morning and will hopefully stick, changed macOS Chromium builds to use the macOS 11 SDK and tools from Xcode 12.2rc. Previously, we were using this SDK and these tools for mac-arm64 builds. This change will switch mac-x86_64 to the same SDK and tools, and we hope that the two architectures will never diverge again.

Embedders should consider upgrading to Xcode 12.2, which is currently a release candidate. With proper Apple Developer access, you’ll find Xcode at https://developer.apple.com/download/. Some macOS 11 compatibility hacks that were necessary in Chromium when building with older SDKs are being removed, so if developing or testing on macOS 11, you will definitely want to be on the new SDK.

More Chromium-specific details are here.

Mark