[!354] Properly use SOURCES in dune_add_library

Merge branch 'use-SOURCES-in-dune-add-library' into 'master'

ref:core/dune-grid dune_add_library implicitly treats all unclaimed trailing
arguments as source file names, but explicitly marking those as SOURCE makes
the code more readable.

See merge request [!354]

  [!354]: gitlab.dune-project.org/core/dune-grid/merge_requests/354

dune/grid/albertagrid/CMakeLists.txt

@@ -10,7 +10,7 @@ if(ALBERTA_FOUND)
   # create dimension dependent alberta libraries
   foreach(_dim ${ALBERTA_WORLD_DIMS})
     list(APPEND ALBERTAGRID_LIBS albertagrid_${_dim}d)
-    dune_add_library(albertagrid_${_dim}d OBJECT ${ALBERTAGRID_SOURCES})
+    dune_add_library(albertagrid_${_dim}d OBJECT SOURCES ${ALBERTAGRID_SOURCES})
   endforeach(_dim RANGE 1 9)
 endif(ALBERTA_FOUND)
 

dune/grid/io/file/dgfparser/CMakeLists.txt

@@ -2,7 +2,7 @@ add_subdirectory(blocks)
 add_subdirectory(test)
 add_subdirectory(utils)
 
-dune_add_library(dgfparser OBJECT dgfparser.cc dgfug.cc)
+dune_add_library(dgfparser OBJECT SOURCES dgfparser.cc dgfug.cc)
 
 install(FILES
   dgfexception.hh

dune/grid/io/file/dgfparser/blocks/CMakeLists.txt

 dune_add_library(dgfparserblocks
-  OBJECT basic.cc  boundarydom.cc  boundaryseg.cc
+  OBJECT
+  SOURCES basic.cc  boundarydom.cc  boundaryseg.cc
     cube.cc  dim.cc  general.cc  gridparameter.cc
     interval.cc  periodicfacetrans.cc projection.cc simplex.cc  simplexgeneration.cc  vertex.cc)
 #add_dune_mpi_flags(dgfparserblocks)

dune/grid/onedgrid/CMakeLists.txt

@@ -18,6 +18,7 @@ install(FILES ${HEADERS} DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/dune/grid/onedg
 exclude_from_headercheck( onedgridleafiterator.hh onedgridleveliterator.hh onedgridhieriterator.hh )
 
 dune_add_library(onedgrid OBJECT
+  SOURCES
   onedgrid.cc
   onedgridfactory.cc
   nulliteratorfactory.cc)

dune/grid/uggrid/CMakeLists.txt

 if(dune-uggrid_FOUND)
   dune_add_library("uggrid" OBJECT
+    SOURCES
     uggridintersections.cc
     uggrid.cc
     uggridentity.cc