Add `$LOAD_PATH` for RuboCop cops.

Library/Homebrew/global.rb

Library/Homebrew/load_path.rb

Library/Homebrew/rubocops.rb

Library/Homebrew/rubocops/caveats_cop.rb

Library/Homebrew/rubocops/checksum_cop.rb

Library/Homebrew/rubocops/class_cop.rb

Library/Homebrew/rubocops/components_order_cop.rb

Library/Homebrew/rubocops/components_redundancy_cop.rb

Library/Homebrew/rubocops/conflicts_cop.rb

Library/Homebrew/rubocops/dependency_order_cop.rb

Library/Homebrew/rubocops/extend/formula_cop.rb

Library/Homebrew/rubocops/formula_desc_cop.rb

Library/Homebrew/rubocops/homepage_cop.rb

Library/Homebrew/rubocops/lines_cop.rb

Library/Homebrew/rubocops/options_cop.rb

Library/Homebrew/rubocops/patches_cop.rb

Library/Homebrew/rubocops/text_cop.rb

Library/Homebrew/rubocops/urls_cop.rb

Library/Homebrew/tap.rb

Library/Homebrew/test/rubocops/caveats_cop_spec.rb