[arccore,message_passing_mpi] Allow adding explicit libraries to 'arccore_message_passing_mpi'.

This will be used for example to add libraries to handle specific features
like GPU aware. This is needed with Cray Mpich.

Author: grospelliergilles

arccore/src/message_passing_mpi/arccore/message_passing_mpi/CMakeLists.txt

@@ -8,10 +8,12 @@ endif()
 
 # On a besoin du support de MPI 3.1
 if (NOT WIN32)
-  if (MPI_CXX_VERSION VERSION_LESS "3.1")
-    message(FATAL_ERROR "MPI Version (${MPI_CXX_VERSION}) is too old. Version 3.1 is required."
-      " Add -DARCCORE_USE_MPI=NO to cmake configuration to compile without MPI."
-    )
+  if (MPI_CXX_VERSION)
+    if (MPI_CXX_VERSION VERSION_LESS "3.1")
+      message(FATAL_ERROR "MPI Version (${MPI_CXX_VERSION}) is too old. Version 3.1 is required."
+        " Add -DARCCORE_USE_MPI=NO to cmake configuration to compile without MPI."
+      )
+    endif()
   endif()
 endif()
 
@@ -50,3 +52,6 @@ arccore_add_component_library(message_passing_mpi
 
 target_link_libraries(arccore_message_passing_mpi PUBLIC arccore_trace arccore_message_passing arccore_collections arccore_concurrency)
 target_link_libraries(arccore_message_passing_mpi PUBLIC arcconpkg_MPI)
+if (ARCCORE_ADDITIONAL_MPI_LIBRARIES)
+  target_link_libraries(arccore_message_passing_mpi PUBLIC ${ARCCORE_ADDITIONAL_MPI_LIBRARIES})
+endif()