VCPKG_INSTALLATION_ROOT env variable not available

[giallu]

This documentation:
https://github.com/actions/runner-images/blob/win22/20231023.1/images/win/Windows2022-Readme.md#environment-variables

promises an environment variable VCPKG_INSTALLATION_ROOT. However, when I try to use this in a build step like so:

- name: Configure CMake
  if: runner.os == 'Windows'
  run: cmake -S . -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} --toolchain="${{env.VCPKG_INSTALLATION_ROOT}}/scripts/buildsystems/vcpkg.cmake"

The variable seems to be not there. I tried a few variations:

• ${{env.VCPKG_INSTALLATION_ROOT}}
• $VCPKG_INSTALLATION_ROOT

Originally posted by @mcourteaux in #6376 (comment)

[giallu]

I noticed the issue with an Ubuntu 22.04 runner, I double checked with a windows-2019 runner and there it seems to be correctly added to the env