github: + missing callback dep

.github/workflows/main.yml

@@ -123,6 +123,25 @@ jobs:
 
     # ----------------------------------------------------------------
 
+    - name: Clone callback
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-callback
+        path: repo/callback
+
+    - name: Configure callback
+      # configure cmake for callback in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_callback -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/callback
+
+    - name: Build callback
+      run: cmake --build ${{github.workspace}}/build_callback --config ${{env.BUILD_TYPE}}
+
+    - name: Install callback
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_callback
+
+    # ----------------------------------------------------------------
+
     - name: Clone webutil
       uses: actions/checkout@v3
       with: