fix for error in the case of UNC syntax in PATH

[Lutger]

Dub fails with the exception "Empty path entries not allowed" when there is an UNC path entry in the PATH environment variable. This is because the UNC syntax '\server\share\path' is treated as starting with an empty path entry.

[s-ludwig]

Shouldn't this be if( path.startsWith("\\\\") )?

[Lutger]

you're right, I'm sorry I was too hasty to commit this.

[s-ludwig]

Does Path.toNativeString() produce anything useful for UNC paths with the fix? It looks like it would omit the leading backslashes and thus probably make dub fail at a later stage. But in any case, I'll also add a bunch of unit tests including UNC paths to make this more robust for the future.

[Lutger]

Indeed, I should have posted this as an issue instead as I haven't looked at all the consequences.

Dub would fail in a later stage, but only if an UNC path is actually used. At the moment dub fails in my environment in all cases because I have an UNC path parsed by dub at startup.

I have added a further fix, but it's a bit hackish and most likely there are some syntaxes not supported by it.

[s-ludwig]

Okay, thanks. I'll merge this for now and think about it some more later on (other possibilities: allow empty path entries or having an isUNC property).