hgarrereyn, sorry for the late reply.
I double-checked, everything is fine on Linux with the nspire-tools command. The Makefile and main.c should be created in your current folder.
I don't know if this is an issue with the Docker setup or the nspire-tools command itself. Most developers are using Linux, some are using Windows, but not MacOS X, so things haven't been thoroughly tested on it, and I can't really troubleshoot myself MacOS X issues...