btm/chef — comment on commit d98cb66196e468e93f5220597bddc2be0e018db8
File: chef/lib/chef/provider/package/rubygems.rb line 340
By btm:

::File::PATH_SEPARATOR correctly provides the separator used in PATHs, which is ':' on unix and ';' on windows.

File.join still joins with '/' on windows because that is the value of SEPARATOR, but windows paths are separated with a back-slash, which is the value of ALT_SEPARATOR.