add a workflow to test build on previous versions of ubuntu: 20.04

.github/workflows/build-ubuntu20-04.yml

@@ -0,0 +1,43 @@
+name: build
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+env:
+  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
+  BUILD_TYPE: Debug
+
+jobs:
+  build:
+    # The CMake configure and build commands are platform agnostic and should work equally
+    # well on Windows or Mac.  You can convert this to a matrix build if you need
+    # cross-platform coverage.
+    # See: https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/managing-complex-workflows#using-a-build-matrix
+    runs-on: ubuntu-20.04
+
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        submodules: true
+    # install dependencies
+    - name: Install dependencies
+      run: sudo apt-get update && sudo apt-get install -yq libfl-dev ninja-build #clang
+      #run: sudo apt-get update #&& sudo apt-get install -yq libboost-dev capnproto libcapnp-dev ninja-build clang
+
+    - 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
+      run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -GNinja -DCMAKE_C_COMPILER=clang -DENABLE_SANITIZERS=ON
+
+    - name: Build
+      # Build your program with the given configuration
+      run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
+
+    - name: Test
+      working-directory: ${{github.workspace}}/build
+      # Execute tests defined by the CMake configuration.  
+      # See https://cmake.org/cmake/help/latest/manual/ctest.1.html for more detail
+      run: ctest -VV -C ${{env.BUILD_TYPE}}