Users may want to play around with gpt4all-j from the command line. But they may not have Qt, and might not want to get it, or may find it very hard to do so - eg when using a Google Colab or similar hosted service.
It's easy to build the CLI tools just by building the `ggml` sub folder. So this commit adds instructions on doing that, including an example invocation of the `gpt-j` binary.
I'm not sure if it was intentional that the build instructions tell the user to clone `manyoso/gpt4all-chat.git`?
But I would think this should be cloning the main repo at `nomic-ai/gpt4all-chat` instead. Otherwise users following this command might get changes not yet merged into the main repo, which could be confusing.