fix: fix for building

mix.exs

@@ -2,6 +2,8 @@ defmodule BDS.MixProject do
   use Mix.Project
 
   def project do
+    ensure_xla_compiler_flags()
+
     [
       app: :bds,
       version: "0.1.0",
@@ -15,6 +17,22 @@ defmodule BDS.MixProject do
     ]
   end
 
+  # XLA 0.9.x headers (pulled by exla) illegally specialize `std::is_signed`,
+  # which Apple clang 17+/libc++ rejects with a hard `-Winvalid-specialization`
+  # error, breaking the exla NIF build. Disable just that diagnostic on macOS so
+  # the C++ compile succeeds. Guarded to Darwin so the Linux/gcc build path is
+  # untouched. Appends rather than overwrites any CFLAGS the caller already set.
+  defp ensure_xla_compiler_flags do
+    if :os.type() == {:unix, :darwin} do
+      flag = "-Wno-invalid-specialization"
+      current = System.get_env("CFLAGS", "")
+
+      unless String.contains?(current, flag) do
+        System.put_env("CFLAGS", String.trim(flag <> " " <> current))
+      end
+    end
+  end
+
   def application do
     [
       extra_applications: [:logger, :wx, :ssl],