(build) Add required SDK for CodeQL

This is no longer installed by default on GitHub Actions runner, so need
to manually install it.

Author: gep13

.github/workflows/codeql-analysis.yml

@@ -39,7 +39,10 @@ jobs:
     - run: git checkout HEAD^2
       if: ${{ github.event_name == 'pull_request' }}
 
-    # Initializes the CodeQL tools for scanning.
+    - name: Install .NET Core SDK (global.json)
+      uses: actions/setup-dotnet@v4.3.1
+
+      # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v1
       with: