Build a simple kernel to compare intel compiler and clang in simple environment

benchmarks/Grid_su3_test.cc

@@ -0,0 +1,10 @@
+#include <Grid.h>
+
+using namespace std;
+using namespace Grid;
+using namespace Grid::QCD;
+
+void su3_test_mult(LatticeColourMatrix &z, LatticeColourMatrix &x,LatticeColourMatrix &y)
+{
+  z=x*y;
+}