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.

Bots and Googlers, in most cases, use the hermetic toolchain instead of a systemwide Xcode installation, and will not need to take any action.

If you’re using an installed copy of Xcode instead of the hermetic toolchain, you 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.

Developers who have been working on mac-arm64 may have a mac_xcode_version custom_var in their .gclient. This setting is obsolete and should be removed. The target_cpu gn argument is still necessary.

Mark