osu: add an experiment for Intel MPI tunning

garlic/exp/index.nix

@@ -101,6 +101,7 @@
     latencyMt = latency.override { enableMultithread = true; };
     latencyMtShm = latency.override { enableMultithread = true; interNode = true; };
     bw = callPackage ./osu/bw.nix { };
+    impi = callPackage ./osu/impi.nix { };
     bwShm = bw.override { interNode = false; };
   };
 }