ci/appveyor: Run builds on x64 platform
ci/appveyor: Run builds on x64 platform

  The newest versions of Elm don't support x86 platforms anymore so we
  need to run our builds on an x64 platform in order to even download
  the `elm` binary.

  We also need to install a specific version of Node to get a x64 build
  on AppVeyor since by default they provide a x86 version.

cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop