CI: build Linux in static and shared versions

This is the most likely (only) platform where building dynamically might be used.

.github/workflows/linux-gcc13.yaml

@@ -7,8 +7,15 @@ on:
 
 jobs:
   build_libmatroska:
-    name: libmatroska with gcc13
+    name: libmatroska ${{ matrix.shared.name }} with gcc13
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        shared: [
+          { "name": "Dynamic", "option": "ON"},
+          { "name": "Static",  "option": "OFF"}
+        ]
     env:
       CMAKE_OPTIONS: -DCMAKE_CXX_EXTENSIONS=OFF
       CMAKE_MATROSKA_OPTIONS: -DBUILD_EXAMPLES=ON
@@ -25,8 +32,8 @@ jobs:
           path: libebml
           # minimum version we support ref: 'release-1.4.3'
 
-      - name: Configure libebml
-        run: cmake -S libebml -B libebml/_build ${{ env.CMAKE_OPTIONS }}
+      - name: Configure ${{ matrix.shared.name }} libebml
+        run: cmake -S libebml -B libebml/_build ${{ env.CMAKE_OPTIONS }} -DBUILD_SHARED_LIBS=${{ matrix.shared.option }}
         env:
           CC:  gcc-13
           CXX: g++-13
@@ -37,8 +44,8 @@ jobs:
       - name: Install libebml
         run: cmake --install libebml/_build --prefix ${GITHUB_WORKSPACE}/_built
 
-      - name: Configure CMake
-        run: cmake -S . -B _build  ${{ env.CMAKE_OPTIONS }} ${{ env.CMAKE_MATROSKA_OPTIONS }} -DEBML_DIR="${GITHUB_WORKSPACE}/_built/lib/cmake/EBML"
+      - name: Configure ${{ matrix.shared.name }} libmatroska
+        run: cmake -S . -B _build  ${{ env.CMAKE_OPTIONS }} ${{ env.CMAKE_MATROSKA_OPTIONS }} -DBUILD_SHARED_LIBS=${{ matrix.shared.option }} -DEBML_DIR="${GITHUB_WORKSPACE}/_built/lib/cmake/EBML"
         env:
           CC:  gcc-13
           CXX: g++-13