github: + catch2 install for build

.github/workflows/cmake-single-platform.yml

@@ -22,6 +22,10 @@ jobs:
     steps:
     - uses: actions/checkout@v3
 
+    - name: Install catch2
+      # install catch2.  see [[https://stackoverflow.com/questions/57982945/how-to-apt-get-install-in-a-github-actions-workflow]]
+      run: sudo apt-get install -y catch2
+
     - name: Configure CMake
       # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.
       # See https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html?highlight=cmake_build_type
@@ -36,4 +40,3 @@ jobs:
       # Execute tests defined by the CMake configuration.
       # See https://cmake.org/cmake/help/latest/manual/ctest.1.html for more detail
       run: ctest -C ${{env.BUILD_TYPE}}
-