Revert "Revert "Upgrade to 5.0.71.48"" DO NOT MERGE

This reverts commit f2e3994fa5148cc3d9946666f0b0596290192b0e,
and updates the x64 makefile properly so it doesn't break that
build.

FPIIM-449

Change-Id: Ib83e35bfbae6af627451c926a9650ec57c045605
(cherry picked from commit 109988c7ccb6f3fd1a58574fa3dfb88beaef6632)
diff --git a/test/perf.isolate b/test/perf.isolate
new file mode 100644
index 0000000..77f66cc
--- /dev/null
+++ b/test/perf.isolate
@@ -0,0 +1,23 @@
+# Copyright 2016 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+{
+  'variables': {
+    'command': [
+      '../tools/run_perf.py',
+    ],
+    'files': [
+      '../tools/run_perf.py',
+      # This is often used to trigger performance bots. We include it in the
+      # isolate to not get these builds deduped.
+      '../tools/whitespace.txt',
+      'js-perf-test/',
+      'memory/',
+      'simdjs/',
+    ],
+  },
+  'includes': [
+    'cctest/cctest_exe.isolate',
+    '../src/d8.isolate',
+  ],
+}