Silence #pragma-once native build warning so docs lint passes

The lint CI job runs `mix docs && mix docs 2>&1 | (! grep -q "warning:")`.
The unifex-generated cnode source `_generated/cnode/native.c` begins with
`#pragma once`, and the GCC version now shipped in the CI docker image emits
a `#pragma once in main file` warning when compiling it. GCC has no dedicated
`-Wno-*` flag for this diagnostic, so the only reliable way to keep this
generated-code noise out of the docs warning check is `-w` on the native.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: FelonEkonom

bundlex.exs

@@ -14,7 +14,14 @@ defmodule ExLibnice.BundlexProject do
         deps: [unifex: :unifex],
         os_deps: [nice: :pkg_config],
         interface: [:nif, :cnode],
-        preprocessor: Unifex
+        preprocessor: Unifex,
+        # Silence native build warnings. The unifex-generated cnode `native.c`
+        # starts with `#pragma once`, and newer GCC (in the CI image) emits a
+        # `#pragma once in main file` warning for it. That warning has no
+        # dedicated `-Wno-*` flag in GCC, so the docs lint check
+        # (`mix docs ... | ! grep "warning:"`) would otherwise fail on this
+        # generated-code noise.
+        compiler_flags: ["-w"]
       ]
     ]
   end