I'm not sure I fully understand your question, but you are supposed to put all the arc2c files at the root level, where arc.sh lives, then load arc2c.sh and finally call (compile-file "foo.arc"). Tell me if I didn't answer your question or if you still get something wrong.
Yes, that's what I was looking for: where to put arc2c in the tree.
My next arc2c problems are a) gc.h is missing; do I need to download it somewhere? and b) ‘QUOTE_CONSTANTS’ undeclared - I can't figure out where it gets declared. I'm trying to compile simply "(+ 1 1)".
How do I push changes to the git? "git push" gives me "fatal: The remote end hung up unexpectedly". I set up a ssh public key. Do I need to get authorization from you guys? (I've never done a git push before, so assume I may be doing something stupid.)