function gitClone (cb) {
          const args = ['clone', '--depth', 1, url, folder]
          spawn(GIT, args, { stdio: 'ignore' }, err => {
            if (err) err.message += ` (git clone) (${name})`
            cb(err)
          })
        }
Clones several projects that are known to follow "JavaScript Standard Style" and runs
the `standard` style checker to verify that it passes without warnings. This helps
ensure we don't accidentally introduce new style rules that cause previously "good"
code to start failing with new warnings! (And if we do, then that needs to be a MAJOR
VERSION BUMP.)