Upgrade clang to 16.0.3

We really want clang 17 for the new CUDA version, but that isn't out
yet.  This gets us a lot closer.

Change-Id: Iff6bb187260777690ae68a7eaef1e508c7194e68
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/WORKSPACE b/WORKSPACE
index c603581..0c98e3f 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -251,11 +251,11 @@
 
 load("@com_grail_bazel_toolchain//toolchain:rules.bzl", "llvm", "llvm_toolchain")
 
-llvm_version = "13.0.0"
+llvm_version = "16.0.3"
 
 llvm(
     name = "llvm_k8",
-    distribution = "clang+llvm-%s-x86_64-linux-gnu-ubuntu-16.04.tar.xz" % llvm_version,
+    distribution = "clang+llvm-%s-x86_64-linux-gnu-ubuntu-22.04.tar.xz" % llvm_version,
     llvm_version = llvm_version,
 )