[cmake][bugfix] Fix the testsuite for sequential builds

Some tests assume MPI being present, although they are not executed in parallel. This information got lost in the transition to dune_add_test and is restored with this patch. Thanks to @markus.blatt for noticing.

This fixes #13 (closed)

dune/istl/paamg/test/CMakeLists.txt

@@ -64,20 +64,26 @@ endif()
 
 dune_add_test(SOURCES twolevelmethodtest.cc)
 
-dune_add_test(SOURCES galerkintest.cc)
 dune_add_test(SOURCES graphtest.cc)
-dune_add_test(SOURCES hierarchytest.cc)
-dune_add_test(SOURCES kamgtest.cc)
-
-dune_add_test(NAME pamg_comm_repart_test
-              SOURCES parallelamgtest.cc
-              COMPILE_DEFINITIONS -DAMG_REPART_ON_COMM_GRAPH)
 
-dune_add_test(NAME pamgtest
-              SOURCES parallelamgtest.cc)
+dune_add_test(SOURCES kamgtest.cc)
 
 dune_add_test(SOURCES transfertest.cc)
 
 dune_add_test(NAME twolevelmethodschwarztest
               SOURCES twolevelmethodtest.cc
               COMPILE_DEFINITIONS USE_OVERLAPPINGSCHWARZ)
+
+# These tests need MPI, even though they are only run sequentially
+if(MPI_FOUND)
+  dune_add_test(SOURCES galerkintest.cc)
+
+  dune_add_test(SOURCES hierarchytest.cc)
+
+  dune_add_test(NAME pamgtest
+                SOURCES parallelamgtest.cc)
+
+  dune_add_test(NAME pamg_comm_repart_test
+                SOURCES parallelamgtest.cc
+                COMPILE_DEFINITIONS -DAMG_REPART_ON_COMM_GRAPH)
+endif()
\ No newline at end of file