ci/windows: Use 2 container stages

The first container stage ("build") is for dependencies of the build.
These are infrequently-changing things like Visual Studio, LLVM, git,
and also meson. The second container stage ("test") currently depends
on the first, and adds test dependencies like piglit.

This lets us rev piglit without having to rebuild LLVM.

Acked-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14637>

.gitlab-ci/windows/mesa_container.ps1

@@ -6,6 +6,8 @@ $registry_username = $args[1]
 $registry_password = $args[2]
 $registry_user_image = $args[3]
 $registry_central_image = $args[4]
+$build_dockerfile = $args[5]
+$registry_base_image = $args[6]
 
 Set-Location -Path ".\.gitlab-ci\windows"
 
@@ -39,7 +41,7 @@ if ($?) {
 }
 
 Write-Host "No image found at $registry_user_image or $registry_central_image; rebuilding"
-docker --config "windows-docker.conf" build --no-cache -t "$registry_user_image" .
+docker --config "windows-docker.conf" build --no-cache -t "$registry_user_image" -f "$build_dockerfile" --build-arg base_image="$registry_base_image" .
 if (!$?) {
   Write-Host "Container build failed"
   docker --config "windows-docker.conf" logout "$registry_uri"