Ios compile (#784)

* try to fix build for ios

* skip cpu compile

* fix namespace

* fix namespace

* Use CMake for platform specific cpu compile

---------

Co-authored-by: Angelos Katharopoulos <a_katharopoulos@apple.com>

mlx/compile_impl.h

@@ -0,0 +1,11 @@
+// Copyright © 2023-2024 Apple Inc.
+
+#pragma once
+
+#include "mlx/device.h"
+
+namespace mlx::core::detail {
+
+bool compile_available_for_device(const Device& device);
+
+}