This method is pretty huge. I really think there's enough going on here for this to be its own class, and definitely could at least be different methods that operate at different levels of abstraction. For example, each inline comment can basically be made into a method name so the top level method looks like:
```ruby
def build_dmg
  create_dmg_stage_dir
  copy_pkg_to_dmg_stage
  copy_assets_to_dmg_stage
  create_writeable_dmg
  attach_dmg
  set_volume_icon
  customize_dmg_appearance
  set_dmg_icon
end
```