Unlike Linux, Windows cannot reuse the freedesktop ci-templates as they exist as we do not have Podman, Skopeo, or even Docker-in-Docker builds available under Windows.
We still reuse the same model: build a base container with the core operating system and infrequently-changed build dependencies, then execute Mesa builds only inside that base container. This is open-coded in PowerShell scripts.
The base container build job executes the mesa_container.ps1 script which reproduces the ci-templates behaviour. It looks for the registry image in the user's namespace, and exits if found. If not found, it tries to copy the same image tag from the upstream Mesa repository. If that is not found, the image is rebuilt inside the user's namespace.
The rebuild executes docker build which calls mesa_deps.ps1 inside the container to fetch and install all build dependencies. This includes Visual Studio Community Edition (downloaded from Microsoft, under the license which allows use by open-source projects), other build tools from Chocolatey, and finally Meson and Python dependencies from PyPI.
This job is executed inside a Windows shell environment directly inside the host, without Docker.
The Mesa build runs inside the base container, executing mesa_build.ps1. This simply compiles Mesa using Meson and Ninja, executing the build and unit tests. Currently, no build artifacts are captured.