Change exclude to use `**` to skip levels
Backporting from to-be merged upstream MR https://github.com/chef/omnibus/pull/834.
Here we specify File::FNM_PATHNAME to the fnmatch call, so 'start/*/end' still matches 'start/middle/end', but you need 'start/**/end' if you want to match 'start/on/the/way/to/the/end'
Edited by Dustin Collins