supporting macos?

Author: pancetta

.github/workflows/ci_pipeline.yml

@@ -36,12 +36,13 @@ jobs:
           flakeheaven lint --benchmark pySDC
 
   user_cpu_tests:
-    runs-on: ubuntu-latest
-
     strategy:
       matrix:
         python: ['3.7', '3.8', '3.9', '3.10']
         env: ['base', 'fenics', 'mpi4py', 'petsc']
+        os: ['macos-12', 'ubuntu-latest']
+
+    runs-on: ${{ matrix.os }}
 
     defaults:
       run:
@@ -65,7 +66,7 @@ jobs:
 
       - name: Uploading artifacts
         uses: actions/upload-artifact@v3
-        if: matrix.python == '3.10'
+        if: matrix.python == '3.10' &&  matrix.os == 'ubuntu-latest'
         with:
           name: cpu-test-artifacts
           path: |