def header_dirs
      real = @base_dir.realpath
      all_files = Find.find(real).map { |f| Pathname.new(f) }.reject(&:directory?)
      unbundled = all_files.reject { |path| vendor_bundle?(path) }
      files = unbundled.select { |path| HPP_EXTENSIONS.include?(path.extname.downcase) }
      files.map(&:dirname).uniq
    end
def header_dirs
      real = @base_dir.realpath
      all_files = Find.find(real).map { |f| Pathname.new(f) }.reject(&:directory?)
      unbundled = all_files.reject { |path| vendor_bundle?(path) }
      files = unbundled.select { |path| HPP_EXTENSIONS.include?(path.extname.downcase) }
      files.map(&:dirname).uniq
    end
Find all directories in the project library that include C++ header files
 @return [Array<Pathname>]