[boost] Re: [filesystem] New errors on Cygwin

Andrey Semashev wrote:

But here is the question: do we actually want to consistently treat Cygwin as a POSIX platform across Boost libraries?

While the patch to System is a fairly disruptive change, and I did know that, I applied it without hesitation because this patch is also applied by the Cygwin project to their Boost packages. So I figured that if they're going to do it anyway, we might as well, too. I can't think of a reason for us to do something different on Cygwin.