Change so that Python library can be built w/ or w/o yggdrasil

Update build so that ePhotosynthesis can be build against yggdrasil in isolation without compiling the interface separately
Install MPI for non-mpi build test

Author: langmm

.github/workflows/test-suite.yml

@@ -160,6 +160,10 @@ jobs:
           yggconfig
           yggcompile cpp
           ygginfo
+      - name: Install mpi with non-mpi Sundials to test compilation
+        if: matrix.with-mpi == false
+        run: |
+          conda install openmpi -y
       - name: Install specific version of Sundials via conda
         if: matrix.sundials-version != 'latest' && matrix.with-mpi == false
         run: |