Add error-handling, whitespace-safety, and Rosetta support to scripts/ccl & scripts/ccl64

[gwerbin]

I noticed that on my ARM Mac system, the ccl64 script had a fall-through case, which led to un-set shell parameters and eventually a confusing error message.

This PR patches the ccl and ccl64 scripts to avoid such errors.

I also hard-coded Rosetta support into the case tree by using the x86-64 settings when ARM64 is detected and the environment variable CCL_USE_ROSETTA=1. I thought it was safer to require "opt-in" than "opt-out", given that there are apparently some problems running CCL under Rosetta (e.g. https://github.com/Clozure/ccl/issues/356).