Update build pipeline to include .NET 9 SDK

.github/workflows/build.yml

@@ -21,6 +21,10 @@ jobs:
       TEST_RESULT_DIR: drop\testresults
     steps:
       - uses: actions/checkout@v1
+      - name: Setup dotnet
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.0.x'
       - name: Build Everything
         shell: powershell
         run: ./build.ps1