bug fix: Alter Makefile to compile with MVAPICH2

Makefile

@@ -951,6 +951,7 @@ $(MULTIVERSO_LIB):
 	@mkdir -p $(BINDIR)
 	@mkdir -p $(SOURCEDIR)/Multiverso/build/$(BUILDTYPE)
 	@cmake -DCMAKE_VERBOSE_MAKEFILE=TRUE \
+		-DCMAKE_CXX_COMPILER=$(CXX) \
 		-DOpenMP_CXX_FLAGS="" \
 		-DOpenMP_C_FLAGS="" \
 		-DBoost_NO_BOOST_CMAKE=TRUE \