Build needs .NET9 SDK

Author: JohnySeven

.github/workflows/continuous.yml

@@ -24,8 +24,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: 'Cache: .nuke/temp, ~/.nuget/packages'
-        uses: actions/cache@v4
+        name: 'Cache: .nuke/temp, ~/.nuget/packages'
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.0.x'
+      - uses: actions/cache@v4
         with:
           path: |
             .nuke/temp