bpo-42056: macOS - allow arm64 as a supported arch by mistydemeo · Pull Request #22732 · python/cpython
This section of the configure script only accepts Intel and PowerPC as valid architectures, but Apple's new ARM Macs means that arm64 can occur too. Without this, configure will fail with the message Unexpected output of 'arch' on OSX.
I didn't include a 32-bit option since Apple no longer ship any devices that support 32-bit ARM. Apple's ARM Macs are 64-bit only.