Update clang flags for latest AOSP master

Change-Id: I492b5a4b87689f4eb95466fc92241a0f88415012
diff --git a/cc/clang.go b/cc/clang.go
index c348eea..6b25d4f 100644
--- a/cc/clang.go
+++ b/cc/clang.go
@@ -11,6 +11,7 @@
 	"-finline-limit=64",
 	"-fno-canonical-system-headers",
 	"-fno-tree-sra",
+	"-fprefetch-loop-arrays",
 	"-funswitch-loops",
 	"-Wmaybe-uninitialized",
 	"-Wno-error=maybe-uninitialized",