Adding an option to Build-Module for sorting source files

[gaelcolas]

fixes #118 This is the flexible approach so we can have more customized sorting mechanism.

The alternative is that we mandate the sorting by always adding | Sort-Object -Property 'FullName' to the Get-ChildItem.

TBH, I prefer the latter since:

1. the perf impact will be minimum anyway
2. there's no need to change how we call Build-Module,
3. It's the same behaviour for NTFS file systems...

but it's also a bit more risky as it changes the code path, and is less flexible (although, we may not need to be too clever anyway). Let me know and I can amend the PR with your suggestion. I'd love to get that sorted and published "soon", so my build can be fixed (and finally OSS'ed..). Thanks, Gael

[Jaykul]

I'm OK merging it the way you've written it -- that's guaranteed not to have any side effects, but I agree with your points -- it seems to me that putting the sort in (although it will have a tiny performance impact) is safe enough.

As you say, it won't really change the outcome except in this edge case where the outcome is unexpectedly unpredictable and breaks things.

[gaelcolas]

I'll favour #120 as it keeps the change simpler and doesn't affect the UX. If needed we can fall back to this more complex approach.