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/third_party/pico-sdk/tools/pioasm/BUILD b/third_party/pico-sdk/tools/pioasm/BUILD
index 355834f..1a276c3 100644
--- a/third_party/pico-sdk/tools/pioasm/BUILD
+++ b/third_party/pico-sdk/tools/pioasm/BUILD
@@ -21,6 +21,7 @@
         "-Wno-unused-parameter",
         "-Wno-sign-compare",
         "-fexceptions",
+        "-Wno-unused-but-set-variable",
     ],
     includes = [
         ".",