Hi, the error message in your posting indicates that the version of LiveCode you are using is wanting to build for ARM64 whilst the version of the external you are using is not targeted for this.
I've no idea if there is a more recent version of rrehardcopy than the one you are using, but if there is one I'd try it! If there isn't, consider using an older version of LC that doesn't build for ARM64
Dave
PS: just checked, the latest copy of rrehardcopy.lcext I can find at
http://downloads.livecode.com/livecode (contained in the LiveCodeSDK-R14 bundle) is dated 27th September 2012. I know that a newer version, compiled by Monte is available as part of the mergext offering available to indy and business customers, so if you have a paid licence you can get it from your LiveCode product page.
If you don't have a paid-for licence then I'm not sure what to do. It doesn't seem to be available on the LiveCode website unless you have an Indy or Business licence - yet Monte offers it as a free download at
http://mergext.com. However you have to be logged in, and possibly a paying customer, before you can access the link. I suggest you go to
http://mergext.com, register a free account and download the new version...
Let us know how you get on