no need to distinguish mpi and nmad at makefile-level

Makefile.am

@@ -39,10 +39,6 @@ if USE_MPI
 SUBDIRS += mpi
 endif
 
-if USE_NMAD
-SUBDIRS += mpi
-endif
-
 if USE_DSM
 SUBDIRS += dsm
 endif

configure.ac

@@ -433,10 +433,7 @@ fi
 AC_MSG_CHECKING(whether the StarPU MPI nmad library should be generated)
 AC_MSG_RESULT($build_nmad_lib)
 
-AC_SUBST(USE_NMAD, $build_nmad_lib)
-AM_CONDITIONAL(USE_NMAD, test x$build_nmad_lib = xyes)
-
-
+AM_CONDITIONAL(USE_MPI, test "x$build_nmad_lib = xyes" -o "x$build_mpi_lib = xyes")
 
 ###############################################################################
 #                                                                             #
@@ -598,8 +595,6 @@ fi
 AC_MSG_CHECKING(whether the StarPU MPI library should be generated)
 AC_MSG_RESULT($build_mpi_lib)
 
-AC_SUBST(USE_MPI, $build_mpi_lib)
-AM_CONDITIONAL(USE_MPI, test x$build_mpi_lib = xyes)
 if test x$build_mpi_lib = xyes -o x$build_nmad_lib = xyes ; then
 	AC_DEFINE(STARPU_USE_MPI,[1],[whether the StarPU MPI library is available])
 	if test x$build_mpi_lib = xyes ; then