Hacking in cloning qtc sources as well

.github/workflows/build.yaml

@@ -246,6 +246,13 @@ jobs:
             endif()
           endif()
 
+      # Just get the Qt Creator sources as well under $GITHUB_WORKSPACE/qtc_src, so your job can access it
+      - uses: actions/checkout@v4
+        with:
+          repository: qt-creator/qt-creator
+          ref: "v$ENV{QT_CREATOR_VERSION}"
+          path: qtc_src
+
       - name: Download Qt Creator
         id: qt_creator
         shell: cmake -P {0}
@@ -307,6 +314,7 @@ jobs:
 
           cmake --preset "${env:CMAKE_PRESET}" `
             -DCMAKE_PREFIX_PATH="${{ steps.qt.outputs.qt_dir }};${{ steps.qt_creator.outputs.qtc_dir }}${prefix_extra}" `
+            -DCMAKE_INCLUDE_PATH="$GITHUB_WORKSPACE/qtc_src/src/libs/3rdparty/syntax-highlighting/autogenerated/include"
 
           cmake --build --preset conan-release