Add DOTNET_ROOT

Author: christophwille

.github/workflows/build-ilspy.yml

@@ -30,7 +30,10 @@ jobs:
       with:
         dotnet-version: '8.0.x'
         dotnet-quality: 'ga'
-    
+      env:
+        DOTNET_INSTALL_DIR: ${{ runner.temp }}/.dotnet
+        DOTNET_ROOT: ${{ runner.temp }}/.dotnet
+
     - name: Add msbuild to PATH
       uses: microsoft/setup-msbuild@v2