wgpu-hal doesn't compile for Vulkan without Metal on Mac

[meyerzinn]

Description

cargo build --features vulkan

error[E0433]: failed to resolve: could not find `metal` in the crate root
   --> wgpu-hal/src/vulkan/instance.rs:454:20
    |
454 |             crate::metal::Surface::get_metal_layer(view as *mut objc::runtime::Object, None)
    |                    ^^^^^ could not find `metal` in the crate root

wgpu-hal/src/vulkan/instance.rs#L454 is the sad line.

Expected vs observed behavior

That almost certainly needs to be pulled into a wgpu-hal/auxil submodule, with all the dependencies set up right

-@cwfitzgerald

Platform

M1 MacBook Air (2020) running Ventura (13.3.1) with the latest Vulkan SDK (1.3.243).

[jinleili]

It seems that this issue cannot be reproduced on the latest trunk branch.

[Wumpf]

confirmed!
as of #3964 we're even running with molten-vk on ci now!
not entirely sure which pr fixed the feature compilation issue but seems to be a bit further back