restrict vcpkg to x64 on appveyor
restrict vcpkg to x64 on appveyor

grzegorzmazur/yacas,grzegorzmazur/yacas,grzegorzmazur/yacas,grzegorzmazur/yacas,grzegorzmazur/yacas,grzegorzmazur/yacas,grzegorzmazur/yacas