appveyor: the opam32 archive is in the APPVEYOR_BUILD_FOLDER
appveyor: the opam32 archive is in the APPVEYOR_BUILD_FOLDER

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@docker.com>

djs55/vpnkit,djs55/vpnkit,djs55/vpnkit,samoht/vpnkit