Add ubuntu matrix for building tests via actions

.github/workflows/build-ubuntu.yml

@@ -16,12 +16,11 @@ env:
         echo "Acquire::ftp::Timeout \"120\";"  | sudo tee -a /etc/apt/apt.conf.d/80-custom
 
 jobs:
-  build-ubuntu-latest-tests:
-    # 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-latest
-
+  build-ubuntu-tests:
+    runs-on: ${{matrix.os}}
+    strategy:
+      matrix:
+        os: [latest, ubuntu-22.04, ubuntu-20.04]
     steps:
     - name: set apt conf
       run: ${{env.APT_SET_CONF}}