Update prebuilts to go1.9rc1 ab/4215840

Test: m -j blueprint_tools
Change-Id: I6e92d224c7b1185c0813593ab11403ef50017916
diff --git a/src/internal/cpu/cpu_ppc64.go b/src/internal/cpu/cpu_ppc64.go
new file mode 100644
index 0000000..5b15150
--- /dev/null
+++ b/src/internal/cpu/cpu_ppc64.go
@@ -0,0 +1,7 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cpu
+
+const CacheLineSize = 128