Reconsider using os-specific delimiter in --include option

[hdgarrood]

Currently pulp build --include foo:bar will attempt to include files from both foo and bar on linux and mac, but on windows it will look for a single directory called foo:bar. The separator is path.delimiter, i.e. colon on linux and mac, and semicolon on windows. This is a bit silly in retrospect. Not quite sure what to do about this right now but I'll leave this here and come back to it later.

[paulyoung]

FWIW I found this after trying pulp build --include foo --include bar which would be os-agnostic

[hdgarrood]

Allowing people to specify options like --include more than once is probably the most sensible thing to do, isn't it?