Cross-compiling for M1 mac from non-M1 mac

[mratsim]

<https://github.com/mratsim/constantine/blob/915f89f/constantine.nimble#L441-L445>
    
    
        compile "lib" & bindingsName & ".dylib.arm", "--cpu:arm64 -l:'-target 
arm64-apple-macos11' -t:'-target arm64-apple-macos11'"
        compile "lib" & bindingsName & ".dylib.x64", "--cpu:amd64 -l:'-target 
x86_64-apple-macos10.12' -t:'-target x86_64-apple-macos10.12'"
        exec "lipo bindings/generated/lib" & bindingsName & ".dylib.arm " &
                 " bindings/generated/lib" & bindingsName & ".dylib.x64 " &
                 " -output bindings/generated/lib" & bindingsName & ".dylib 
-create"
    
    
    Run