OpenMPI is only needed if devel/med was compiled with support for it.

Index: cMake/FreeCAD_Helpers/SetupSalomeSMESH.cmake
--- cMake/FreeCAD_Helpers/SetupSalomeSMESH.cmake.orig
+++ cMake/FreeCAD_Helpers/SetupSalomeSMESH.cmake
@@ -131,15 +131,6 @@ macro(SetupSalomeSMESH)
                         message( FATAL_ERROR "hdf5.h was not found (tested pkg-config ${HDF5_VARIANT}, suggested header location was '${hdf5_include_path}').")
                     endif()
                 endif()
-
-                # Med Fichier can require MPI
-                pkg_search_module(OPENMPI ompi-cxx)
-                add_compile_options(${OPENMPI_CFLAGS})
-                link_directories(${OPENMPI_LIBRARY_DIRS})
-                link_libraries(${OPENMPI_LIBRARIES})
-                if(NOT OPENMPI_FOUND)
-                    message( WARNING "ompi-cxx was not found. Check for error above.")
-                endif()
             endif()
             set(SMESH_INCLUDE_DIR ${CMAKE_SOURCE_DIR}/src/3rdParty/salomesmesh/inc)
 
