Switch integration test to qt6 (#1916)

Keep using Qt5 for Cygwin and CodeQL

* CI: upgrade ubuntu

.github/workflows/codeql.yml

@@ -2,7 +2,7 @@ name: "CodeQL"
 
 on:
   push:
-    branches: [ 'master', '1.6.x' ]
+    branches: [ 'master', '1.9.x' ]
   pull_request:
     # The branches below must be a subset of the branches above
     branches: [ 'master' ]
@@ -12,7 +12,7 @@ on:
 jobs:
   analyze:
     name: Analyze
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     permissions:
       actions: read
       contents: read
@@ -28,7 +28,10 @@ jobs:
       uses: actions/checkout@v4
       with:
         submodules: true
-    - run: source .github/ubuntu_deps.sh
+    - run: |
+        source .github/ubuntu_deps.sh
+        sudo apt-get remove -y qt6-base-dev
+        sudo apt-get install -y qtbase5-dev
       
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v3
@@ -36,6 +39,8 @@ jobs:
         languages: ${{ matrix.language }}
 
     - run: source .github/build.sh
+      env:
+        ZNC_QT_VER: "5"
 
     - name: Perform CodeQL Analysis
       uses: github/codeql-action/analyze@v3