static _setup(ui) {
    const exec = require('child_process').exec;
    const symlinkOrCopy = require('symlink-or-copy');

    return new WindowsSymlinkChecker(ui, /^win/.test(process.platform), symlinkOrCopy.canSymlink, exec);
  }
sets up a WindowsSymlinkChecker

providing it with defaults for:

* if we are on windows
* if we can symlink
* a reference to exec

@private
@method _setup
@param UI {UI}
@return {WindowsSymlinkChecker}