The build machinery assumes that the compiler that's used
to build on macOS includes an SDK that's at least as new
as the OS version on the build machine. Explicitly mention
this in Mac/README.txt.
This allows reliably forcing macOS universal2 framework builds
to run under Rosetta 2 Intel-64 emulation on Apple Silicon Macs
if needed for testing or when universal2 wheels are not yet
available.
Co-authored-by: Lawrence D’Anna <lawrence_danna@apple.com>
* Add support for macOS 11 and Apple Silicon (aka arm64)
As a side effect of this work use the system copy of libffi on macOS, and remove the vendored copy
* Support building on recent versions of macOS while deploying to older versions
This allows building installers on macOS 11 while still supporting macOS 10.9.
