I don't use Mac but I've successfully done it for fedora/arm64. At least I think so.
Basically you'll need to cross-compile the compiler (from Nim) into C sources (by specifying the `--os` and `--cpu` options), then move the generated C files to the target machine, using a C compiler installed there to do the remaining tasks. Commands for C compiler and linker can be found in a json file generated during the cross-compilation. The config files are also needed (probably with some of them written). Nimble has to be cross-compiled, either. Because it requires the `compiler` package which needs `nimble` to install.
