github: Install WDK together with WinSDK and MSVC

Install WDK using the official online installer
from the Microsoft website.

Enable WDK tests in GitHub Actions for Linux only.

.github/workflows/build.yml

@@ -6,6 +6,8 @@ on:
 env:
   # See <https://wiki.winehq.org/Mono#Versions> before changing.
   WINE_MONO_VERSION: "8.1.0"
+  # From https://learn.microsoft.com/en-us/windows-hardware/drivers/download-the-wdk#download-icon-step-3-install-wdk
+  WDK_INSTALLER_URL: "https://go.microsoft.com/fwlink/?linkid=2249371"
 
 jobs:
   test-msvc-wine-linux:
@@ -23,11 +25,13 @@ jobs:
       - uses: actions/checkout@v3
       - name: Download MSVC
         run: |
-          ./vsdownload.py --accept-license --dest $(pwd)/msvc
+          WDK_INSTALLERS=$(./wdk-download.sh --cache /var/tmp/msvc-wine "$WDK_INSTALLER_URL")
+          echo Downloaded WDK installers to $WDK_INSTALLERS
+          ./vsdownload.py --accept-license --dest $(pwd)/msvc --cache /var/tmp/msvc-wine --with-wdk-installers "$WDK_INSTALLERS"
           ./install.sh $(pwd)/msvc
       - name: Test using the installed tools
         run: |
-          test/test.sh $(pwd)/msvc
+          HAVE_WDK=1 test/test.sh $(pwd)/msvc
       # Intentionally not storing any artifacts with the downloaded tools;
       # the installed files aren't redistributable!