Pass short path names to configure scripts on Windows

[23Skidoo]

In #2946 we changed Cabal to use the standard mechanism when passing the gcc path to configure scripts. Unfortunately, it looks like this feature is still broken (at least on Windows) when the path contains spaces (a bug in Autoconf). A workaround that is confirmed to work is to use short path names. We should change Cabal to do that automatically.

[gbaz]

Of the mechanisms to get short path names in windows, this looks fairly reliable for programmatic use: http://stackoverflow.com/a/21786312/371753

[23Skidoo]

Is GetShortPathName unreliable?

[gbaz]

Calling the function directly should work fine too. I just tend to prefer to shell out rather than deal with more bindings...

[Mistuke]

8.3 short names can be disabled for performance reasons https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#short_vs._long_names
So I don't particularly like this as the default. Isn't there another possible fix?

[23Skidoo]

@Mistuke

8.3 short names can be disabled for performance reasons

The documentation for GetShortPathName says:

If you call GetShortPathName on a path that doesn't have any short names on-disk, the call will succeed, but will return the long-name path instead. This outcome is also possible with NTFS volumes because there's no guarantee that a short name will exist for a given long name.

So it looks like using GetShortPathName will be no worse than status quo when 8.3 names are disabled.