Add CodeQL workflow with manual build

Since `autobuild` did not work, we have to switch to the "advanced"
mode.

Author: marcphilipp

.github/workflows/codeql.yml

@@ -0,0 +1,42 @@
+name: "CodeQL"
+
+on:
+  push:
+    branches: [ "main" ]
+  schedule:
+    - cron: '23 2 * * 4'
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: 'ubuntu-latest'
+    permissions:
+      security-events: write
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: actions
+            build-mode: none
+          - language: java-kotlin
+            build-mode: manual
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - name: 'Set up JDK 21'
+        uses: actions/setup-java@c5195efecf7bdfc987ee8bae7a71cb8b11521c00 # v4.7.1
+        with:
+          java-version: 21
+          distribution: temurin
+      - uses: sbt/setup-sbt@6c68d2fe8dfbc0a0534d70101baa2e0420e1a506 # v1.1.9
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+      - if: matrix.build-mode == 'manual'
+        # TODO compile only, avoid running tests
+        run: java src/Builder.java
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:${{matrix.language}}"