Weird Windows hack for Re-rendering [ci skip]

[jakirkham]

Adds a weird Windows hack for re-rendering. Here we provide a few lines in conda-forge.yml that are left commented, but can be uncommented for Windows re-rendering only.

Basically my suggestion until we have something better is to do the following.

1. Re-render with this commented.
2. Commit all changes.
3. Uncomment matrix section.
4. Re-render again
5. Recomment this section.
6. Only commit appveyor.yml (possibly amending the last re-rendering commit).

This should get us a little closer to a stable process for doing this.

[jakirkham]

@pelson, is there a way ATM to make a matrix OS specific for conda-smithy? I think that would greatly reduce stress of re-renderings on feedstocks like this one using vc. If there isn't don't worry about it, proper handling of vc at the conda-build-all level ( and possibly conda-build @msarahan 😉 ) is far more useful than adding in OS matrix support to conda-forge.yml

[pelson]

@jakirkham - if you want conda-tools/conda-build-all#36 I can resurrect that one. I'd be more than happy to have that one finally ticked off so that we can just express vc as the dependency, and not 'python'...

[jakirkham]

That sounds like a great idea, @pelson. 😄 It is just unclear to me whether we would need to elevate the status of vc in conda-build or not. ( conda/conda-build#1445 )

[jjhelmus]

Seems like a reasonable solution until the tooling around vc is complete.