[SYCL] Fix dependencies for Doxygen job (#1206)

configure.py requires Ninja to be installed on build machine, which is
missing from default GitHub Actions Linux environments. Install
ninja-build package before proceeding to CMake configuration.

Signed-off-by: Alexander Batashev <alexander.batashev@intel.com>

Author: Alexander Batashev

.github/workflows/gh_pages.yml

@@ -17,7 +17,7 @@ jobs:
         repository: intel/llvm-docs
         path: docs
     - name: Install deps
-      run: sudo apt-get install -y doxygen graphviz ssh
+      run: sudo apt-get install -y doxygen graphviz ssh ninja-build
     - name: Build Docs
       run: |
         mkdir -p $GITHUB_WORKSPACE/build