fix: Enable MPI for github workflow tests.

Author: semi-h

.github/workflows/build_and_test.yml

@@ -41,7 +41,7 @@ jobs:
           >> $GITHUB_PATH
 
     - name: Configure build
-      run: cmake -S . -B build
+      run: FC=mpif90 cmake -S . -B build
 
     - name: Build tests
       run: make -C build