[PATCH 2 of 2] remotefilelog: prevent this extension from loading on Windows

[Augie Fackler]

> On Nov 29, 2018, at 08:18, Yuya Nishihara <yuya at tcha.org> wrote:
> 
> Can't we blacklist them on the buildbot then?
> 
> #require is hard requirement, which make not possible to run the remotefilelog
> tests on Windows.

I'm happy to patch out the #require on a per-test basis as I tackle making them work on Windows. We can switch to a blacklist on the buildbot if you feel strongly, but I'm happy to incur a little extra work on my end so the tests stay obviously-passing for people that aren't working on fixing remotefilelog tests on Windows.