Windows CI: add paraview deps nightly build (#37924)

Add a nightly job to attempt building all Paraview dependencies and
upload the results to cdash. This check doesn't affect the reported
build/test status of Spack. We are using this to monitor the state of
Windows support while working on more-robust checks (eventually the
Windows build will have to succeed to merge PRs to Spack).

.github/workflows/nightly-win-builds.yml

@@ -0,0 +1,31 @@
+name: Windows Paraview Nightly
+
+on:
+  schedule:
+    - cron: '0 2 * * *' # Run at 2 am
+
+defaults:
+  run:
+    shell:
+     powershell Invoke-Expression -Command "./share/spack/qa/windows_test_setup.ps1"; {0}
+
+
+jobs:
+  build-paraview-deps:
+    runs-on: windows-latest
+    steps:
+    - uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab
+      with:
+        fetch-depth: 0
+    - uses: actions/setup-python@d27e3f3d7c64b4bbf8e4abfb9b63b83e846e0435
+      with:
+        python-version: 3.9
+    - name: Install Python packages
+      run: |
+          python -m pip install --upgrade pip six pywin32 setuptools coverage
+    - name: Build Test
+      run: |
+        spack compiler find
+        spack external find cmake ninja win-sdk win-wdk wgl msmpi
+        spack -d install -y --cdash-upload-url https://cdash.spack.io/submit.php?project=Spack+on+Windows --cdash-track Nightly --only dependencies paraview
+        exit 0