Increasing minimum version of macOS required to run gn

[Sylvain Defresne]

Hello all,

Currently gn runs on macOS 10.9. In order to have access to a more conformant libc++ on macOS I'd like to bump this to 10.15. Currently this is to get access to std::aligned_alloc which is part of C++17 (which gn uses) but is not available at runtime on old versions of macOS.

Version 10.15 of macOS corresponds to macOS Catalina released in October 2019.

Chrome and Fuschia already require this version of macOS or higher, but this would have impact on other projects that use gn and support older versions of macOS. Recent versions of Xcode which provides the default toolchain on macOS require a more recent version of macOS (e.g. Xcode 13.0 requires macOS 11.3).

Is requiring macOS 10.15 or higher to run gn blocking?

Regards,

-- Sylvain