Use system zip capablities on Windows about l3build

[josephwright]

Ah, we can close: it got covered by bring zipping 'in house'

[josephwright]

Reference material at https://msdn.microsoft.com/en-us/powershell/reference/5.1/microsoft.powershell.archive/compress-archive makes no mention of dealing with line endings. Probably with PowerShell (or from Lua) we could normalise these, but that seems like quite a step. For the present, perhaps easiest to stick with the approach of using a third-party tool (unless someone else wants to pick this up).

[josephwright]

For the interested, what we currently do is zip up all of the non-binary files with line end normalisation (-ll), then add the binary ones without that. So to use the Windows zip tool we'd have to first normalise line ends in a copy of the source files, then make the zip in one go. That's of course doable by quickly reading/rewriting every file in the area used to build the release, but it seems quite painful.

[pablgonz]

@josephwright Is this still valid?