Make custom target for source files.

dune/solvers/common/CMakeLists.txt

-install(FILES
+set(DUNE_SOLVERS_COMMON
     arithmetic.hh
     boxconstraint.hh
     canignore.hh
@@ -8,4 +8,9 @@ install(FILES
     permutationmanager.hh
     preconditioner.hh
     staticmatrixtools.hh
+)
+
+add_custom_target(dune_solvers_common_sources SOURCES ${DUNE_SOLVERS_COMMON})
+
+install(FILES ${DUNE_SOLVERS_COMMON}
     DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/dune/solvers/common)

dune/solvers/iterationsteps/CMakeLists.txt

-install(FILES
+set(DUNE_SOLVERS_ITERATIONSTEPS
     amgstep.hh
     blockgsstep.cc
     blockgsstep.hh
@@ -27,4 +27,9 @@ install(FILES
     truncatedsaddlepointgsstep.hh
     trustregiongsstep.cc
     trustregiongsstep.hh
+)
+
+add_custom_target(dune_solvers_iterationsteps_sources SOURCES ${DUNE_SOLVERS_ITERATIONSTEPS})
+
+install(FILES ${DUNE_SOLVERS_ITERATIONSTEPS}
     DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/dune/solvers/iterationsteps)