Upgrade to bazel 5.1.1

These are the commands I used to generate the bazel xz file:

    $ wget https://github.com/bazelbuild/bazel/releases/download/5.1.1/bazel-5.1.1-linux-x86_64
    $ xz bazel-5.1.1-linux-x86_64
    $ mv bazel-5.1.1-linux-x86_64.xz bazel_5.1.1.xz

As far as I can tell, we don't need to change anything about our setup
with this upgrade.

Signed-off-by: Philipp Schrader <philipp.schrader@gmail.com>
Change-Id: I1b5335c54b1e91691f157c510a96fcc90fa3ea74
diff --git a/tools/bazel b/tools/bazel
index edb1aca..72ca2f8 100755
--- a/tools/bazel
+++ b/tools/bazel
@@ -24,7 +24,7 @@
   exec "${BAZEL_OVERRIDE}" "$@"
 fi
 
-readonly VERSION="5.0.0"
+readonly VERSION="5.1.1"
 
 readonly DOWNLOAD_DIR="${HOME}/.cache/bazel"
 # Directory to unpack bazel into.  This must change whenever bazel changes.