Fat binary for x86_64 and arm64

Adds support for M1 systems with a fat binary.

If you download the macher file in the assets you will need to make it executable and remove the quarantine flag before it can be run:

% chmod +x macher
% xattr -c macher

Alternatively, download and open the signed and notarized macher.pkg to install macher as /usr/local/bin/macher .