[ci] Add second test suite to cover Doxygen, Fortan, examples

Test Clang besides GCC.
Drop matrix strategy as it is not used.
Do not build in parallel as it makes the output more difficult to read.

.github/workflows/test.yml

@@ -3,27 +3,42 @@ name: Test library
 on: [push, pull_request]
 
 jobs:
-  test:
-    name: Build and test
+  test-minimal-ubuntu:
+    name: Ubuntu minimal build and test
     runs-on: ubuntu-latest
 
-    strategy:
-      matrix:
-        compiler:
-          - gcc
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Install dependencies
+        run: sudo apt-get install cmake clang
+
+      - name: Configure
+        run: cmake -DCMAKE_C_COMPILER=clang -B build
+
+      - name: Build
+        run: cmake --build build
+
+      - name: Test
+        run: ctest --test-dir build --output-on-failure
+
+  test-extended-ubuntu:
+    name: Ubuntu extended build and test
+    runs-on: ubuntu-latest
 
     steps:
       - name: Checkout code
         uses: actions/checkout@v3
 
       - name: Install dependencies
-        run: sudo apt-get install cmake
+        run: sudo apt-get install cmake doxygen gcc gfortran
 
       - name: Configure
-        run: cmake -B build
+        run: cmake -Denable_doc=on -Denable_fortran=on -B build
 
       - name: Build
-        run: cmake --build build --parallel
+        run: cmake --build build
 
       - name: Test
         run: ctest --test-dir build --output-on-failure