mpi/src/Makefile.am: set variable ldflags

mpi/src/Makefile.am

@@ -26,6 +26,8 @@ LIBS = $(top_builddir)/src/@LIBSTARPU_LINK@ @LIBS@ $(FXT_LIBS) $(MAGMA_LIBS)
 AM_CPPFLAGS = -I$(top_srcdir)/include/ -I$(top_srcdir)/src/ -I$(top_builddir)/src -I$(top_builddir)/include -I$(top_srcdir)/mpi/include -I$(top_srcdir)/mpi/src
 AM_LDFLAGS = $(STARPU_OPENCL_LDFLAGS) $(STARPU_CUDA_LDFLAGS) $(STARPU_COI_LDFLAGS) $(STARPU_SCIF_LDFLAGS)
 
+ldflags =
+
 if STARPU_HAVE_WINDOWS
 
 LC_MESSAGES=C