GitLab

Simplify relibc install steps (submodule needs to be updated once relibc commit is in)

See merge request !1232

Include ramfs in initfs

See merge request !1233

update bootstrap.sh for macOS brew using steps from The Book

See merge request !1231

Install cargo-config from bootstrap script

See merge request !1230

Some cookbook entries were failing with an error like this:

```
error: no such subcommand: `config`
```

We can install this subcommand from the bootstrap script, and also
instruct folks in the README to do so manually.