lib/omnibus/fetcher.rb
def create_required_directories
      [
        Config.cache_dir,
        Config.source_dir,
        build_dir,
        project_dir,
      ].each do |directory|
        FileUtils.mkdir_p(directory) unless File.directory?(directory)
      end
    end
def create_required_directories
      [
        Config.cache_dir,
        Config.source_dir,
        build_dir,
        project_dir,
      ].each do |directory|
        FileUtils.mkdir_p(directory) unless File.directory?(directory)
      end
    end
Idempotently create the required directories for building/downloading.
 Fetchers should call this method before performing any operations that
 manipulate the filesystem.

 @return [void]