[Haskell-cafe] Windows Haskell CI

Like ghc itself, we (the Darcs team) also have trouble providing adequate support for Windows. I personally haven't (seriously) used Windows for decades. So I thought we could at least do some automated building and testing for Windows on some CI system, perhaps even automatically build Windows binaries. Is there a free CI service that you could recommend that ideally supports at least Windows, MacOS, and Linux and that has good support for Haskell programs, i.e. some recent ghc and cabal pre-installed? If not, what could be an alternative solution? Any kind of comments or hints are appreciated. Cheers Ben