Fix bug in MPI_CXX_LINK_FLAGS according to variable which

  has leading or trailing whitespace.  This is now an error according to policy CMP0004.

CMakeLists.txt

@@ -306,7 +306,6 @@ if (MORSE_DISTRIB_DIR OR EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/CMakeModules/morse/
     endif()
 
     find_package(MPI REQUIRED)
-
     if (MPI_CXX_INCLUDE_PATH)
       include_directories( ${MPI_CXX_INCLUDE_PATH} )
     endif()
@@ -314,9 +313,10 @@ if (MORSE_DISTRIB_DIR OR EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/CMakeModules/morse/
       set(SCALFMM_CXX_FLAGS "${SCALFMM_CXX_FLAGS} ${MPI_CXX_COMPILE_FLAGS}")
     endif()
     if (MPI_CXX_INCLUDE_PATH)
-      set(SCALFMM_INCLUDES  "${SCALFMM_INCLUDES}; ${MPI_CXX_INCLUDE_PATH}")
+      set(SCALFMM_INCLUDES  "${SCALFMM_INCLUDES};${MPI_CXX_INCLUDE_PATH}")
     endif()
     if (MPI_CXX_LINK_FLAGS)
+      string(REGEX REPLACE " " ";" MPI_CXX_LINK_FLAGS  ${MPI_CXX_LINK_FLAGS} )
       set(SCALFMM_LIBRARIES "${SCALFMM_LIBRARIES};${MPI_CXX_LINK_FLAGS}")
     endif()
     if (MPI_CXX_LIBRARIES)