(ci) GitHub actions fix
(ci) GitHub actions fix

There was a bug in vcpkg.cmake that prevented CMake from seeing installed packages, resolved by https://github.com/microsoft/vcpkg/pull/16293. So go ahead and live at HEAD again, at lease in GitHub Actions, especially as actions/checkout@v2 does not seem to be able to pin vcpkg versions via `git checkout e4ce66e`. 

acgetchell/CDT-plusplus,acgetchell/CDT-plusplus,acgetchell/CDT-plusplus