add guards to ginkgo headers

src/hyteg/ginkgo/GinkgoBlockSolver.hpp

 #pragma once
 
+#include "hyteg/HytegDefinitions.hpp"
+
+#ifdef HYTEG_BUILD_WITH_GINKGO
+
 #include <ginkgo/core/base/mpi.hpp>
 #include <ginkgo/core/log/convergence.hpp>
 #include <ginkgo/core/log/convergence_stream.hpp>
@@ -487,3 +491,5 @@ class GinkgoBlockSolver : public Solver< OperatorType >
 };
 
 } // namespace hyteg
+
+#endif

src/hyteg/ginkgo/GinkgoCGSolver.hpp

 #pragma once
 
+#include "hyteg/HytegDefinitions.hpp"
+
+#ifdef HYTEG_BUILD_WITH_GINKGO
+
+
 #include <memory>
 #include <optional>
 #include <utility>
@@ -21,6 +26,7 @@
 #include "hyteg/p2functionspace/P2ProjectNormalOperator.hpp"
 #include "hyteg/solvers/Solver.hpp"
 
+
 #include "ginkgo/core/factorization/ilu.hpp"
 #include "ginkgo/core/factorization/par_ilu.hpp"
 #include "ginkgo/core/factorization/par_ilut.hpp"
@@ -308,4 +314,6 @@ class GinkgoCGSolver : public Solver< OperatorType >
    rapidjson::Document item_;
 };
 
-} // namespace hyteg
\ No newline at end of file
+} // namespace hyteg
+
+#endif

src/hyteg/ginkgo/GinkgoCommunication.hpp

 #pragma once
 
+#include "hyteg/HytegDefinitions.hpp"
+
+#ifdef HYTEG_BUILD_WITH_GINKGO
+
 #include <memory>
 #include <utility>
 #include <vector>
@@ -83,4 +87,6 @@ void scatter_global_vector( const gko::matrix::Dense< ValueType >*
                       0,
                       comm );
 }
-} // namespace hyteg
\ No newline at end of file
+} // namespace hyteg
+
+#endif

src/hyteg/ginkgo/GinkgoDirichletHandling.hpp

 #pragma once
 
+#include "hyteg/HytegDefinitions.hpp"
+
+#ifdef HYTEG_BUILD_WITH_GINKGO
+
 #include <optional>
 #include <utility>
 #include <vector>
@@ -229,4 +233,6 @@ enum class constraints
    zero_row
 };
 
-} // namespace hyteg
\ No newline at end of file
+} // namespace hyteg
+
+#endif

src/hyteg/ginkgo/GinkgoSparseMatrixProxy.hpp

 #pragma once
 
+#include "hyteg/HytegDefinitions.hpp"
+
+#ifdef HYTEG_BUILD_WITH_GINKGO
+
 #include "core/Abort.h"
 
 #include "hyteg/sparseassembly/SparseMatrixProxy.hpp"
@@ -216,4 +220,6 @@ class GinkgoSparseMatrixProxy : public SparseMatrixProxy
 
    bool is_finialized_;
 };
-} // namespace hyteg
\ No newline at end of file
+} // namespace hyteg
+
+#endif

src/hyteg/ginkgo/GinkgoUtilities.hpp

 #pragma once
 
+#include "hyteg/HytegDefinitions.hpp"
+
+#ifdef HYTEG_BUILD_WITH_GINKGO
+
 #include <ginkgo/core/base/executor.hpp>
 #include <ginkgo/core/base/version.hpp>
 #include <map>
@@ -118,3 +122,5 @@ constexpr std::string_view default_json_cg{R"(
 }
 )"};
 } // namespace hyteg
+
+#endif

src/hyteg/ginkgo/GinkgoVectorProxy.hpp

 #pragma once
 
+#include "hyteg/HytegDefinitions.hpp"
+
+#ifdef HYTEG_BUILD_WITH_GINKGO
+
 #include "core/Abort.h"
 
 #include "hyteg/sparseassembly/SparseMatrixProxy.hpp"
@@ -56,4 +60,6 @@ class GinkgoVectorProxy : public VectorProxy
    gko::dim<2> global_size_;
    gko::distributed::Vector<real_t, int32_t>* vec_;
 };
-}
\ No newline at end of file
+}
+
+#endif