Upgrade to a new Bazel version

This one has better performance and various new features. It also
prevents us from falling too far behind upstream.

Change-Id: I3b8e1c5bda886ea2e990523af9e6de2434c784be
diff --git a/tools/bazel b/tools/bazel
index 415aeff..f6f4c52 100755
--- a/tools/bazel
+++ b/tools/bazel
@@ -24,7 +24,7 @@
   exec "${BAZEL_OVERRIDE}" "$@"
 fi
 
-readonly VERSION="201607070016+7a0d360"
+readonly VERSION="201701021712+4964f2c"
 
 readonly DOWNLOAD_DIR="$(dirname "${BASH_SOURCE[0]}")/../bazel-downloads"
 # Directory to unpack bazel into.  This must change whenever bazel changes.