ci/windows: Artifact Meson build and test logs

These are useful, especially when tests fail. The other jobs do this, so
fall into line.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11261>

.gitlab-ci.yml

@@ -966,6 +966,7 @@ meson-clang:
     - . .\.gitlab-ci\windows\mesa_build.ps1
   artifacts:
     paths:
+      - _build/meson-logs/*.txt
       - _install/
 
 .test-d3d12-windows: