[Build] Make compile with gcc again

src/program_state.hh

@@ -39,7 +39,7 @@ template <class VectorTEMPLATE, class ScalarVectorTEMPLATE> class ProgramState {
 
     using LocalVector = typename Vector::block_type;
     using LocalMatrix = typename Matrix::block_type;
-    auto const dims = LocalVector::dimension;
+    auto constexpr dims = LocalVector::dimension;
 
     // Solving a linear problem with a multigrid solver
     auto const solveLinearProblem = [&](