The documentation explains that when you run 'lb clean', all the generated files are removed except the cache directory. I can confirm that.However, when I run again the build it seems that a lot of packages are downloaded again. Maybe I'm wrong?
Or there's any option to tell lb to use the cache? (I would expect it to be the default though).
I was just wrong, of course.
The build of my image without cache/ takes 50 minutes. When I re-build it it takes about the half.
I was mislead by the download of packages printed on the terminal.