Add basic NetBSD support

[0323pin]

closes #8541
replaces #8679

Tests:
Summary [ 149.522s] 469 tests run: 463 passed, 6 failed, 0 skipped FAIL [ 0.095s] naga::naga snapshots::convert_snapshots_spv FAIL [ 0.387s] wgpu-benchmark::bench/wgpu-benchmark Computepass Encoding FAIL [ 0.386s] wgpu-benchmark::bench/wgpu-benchmark Device::create_bind_group FAIL [ 0.378s] wgpu-benchmark::bench/wgpu-benchmark Device::create_buffer FAIL [ 0.389s] wgpu-benchmark::bench/wgpu-benchmark Renderpass Encoding FAIL [ 0.075s] wgpu-test::wgpu-validation api::instance::multi_instance::multi_instance

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Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.

[0323pin]

FWIW running cargo clippy on NetBSD using Rust-1.91.1 built from source on a clone of wgpu main branch (trunk) where the latest commit is f558612, i.e. without my changes yields the same warning:

[...]
warning: variable does not need to be mutable
   --> wgpu-core/src/instance.rs:267:13
    |
267 |         let mut errors = HashMap::default();
    |             ----^^^^^^
    |             |
    |             help: remove this `mut`
    |
    = note: `#[warn(unused_mut)]` (part of `#[warn(unused)]`) on by default

warning: variable does not need to be mutable
   --> wgpu-core/src/instance.rs:268:13
    |
268 |         let mut surface_per_backend: HashMap<Backend, Box<dyn hal::DynSurface>> =
    |             ----^^^^^^^^^^^^^^^^^^^
    |             |
    |             help: remove this `mut`

    Checking rand v0.8.5
    Checking rand_xorshift v0.3.0
    Checking wayland-protocols-plasma v0.2.0
    Checking nanorand v0.8.0
    Checking spin v0.9.8
warning: this lint expectation is unfulfilled
   --> wgpu-core/src/resource.rs:878:59
    |
878 |                 #[cfg_attr(not(feature = "trace"), expect(clippy::collapsible_if))]
    |                                                           ^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `#[warn(unfulfilled_lint_expectations)]` on by default
[...]

So, this is unrelated to my changes. Is this platform specific?

[ErichDonGubler]

@0323pin:

• RE: unused_mut warnings: The reason that's firing is because Instance::create_surface_from_drm (compiling because NetBSD is a unix) marks those two variables as mut. The vulkan feature is not enabled, so no work is done to actually set those variables (and a surface creation error will unconditionally be returned). I'm not familiar with NetBSD as a platform; is it intended to expose that method? If so, we may need to add a #[cfg_attr(not(vulkan), expect(…))] attribute on those variable declarations (if that's intended) or add more logic specifically that sets those for NetBSD. If not, you'll need to adjust cfg to exclude it on NetBSD.
• RE: unfulfilled_lint_expectations: You can ignore this warning. Once our CI upgrades to a newer Rust version, we'll want to remove it, since the false positive that line is working around will have been fixed in the newer Rust.

EDIT: s/FreeBSD/NetBSD/, SMH at myself

[0323pin]

@ErichDonGubler thanks for the hints. NetBSD doesn't support Vulkan, only OpenGL. So, I would say it should be excluded.

I'll have a look at it tomorrow, need to get some sleep first.

[0323pin]

@ErichDonGubler May I request further pointers? I've changed wgpu-core/src/instance.rs to exclude NetBSD as we don't support Vulkan. I've done this doing the following at lines 254 and 929

    #[cfg(all(
        unix,
        not(target_vendor = "apple"),
        not(target_family = "wasm"),
        not(target_os = "netbsd")
    ))]

But, now clippy complains that:

error[E0599]: no method named `instance_create_surface_from_drm` found for struct `alloc::sync::Arc<wgc::global::Global>` in the current scope
   --> wgpu/src/backend/wgpu_core.rs:812:24
    |
812 |                 self.0.instance_create_surface_from_drm(
    |                 -------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
help: there is a method `instance_create_surface` with a similar name, but with different arguments
   --> /home/pin/Git/wgpu/wgpu-core/src/instance.rs:913:5
    |
913 | /     pub unsafe fn instance_create_surface(
914 | |         &self,
915 | |         display_handle: raw_window_handle::RawDisplayHandle,
916 | |         window_handle: raw_window_handle::RawWindowHandle,
917 | |         id_in: Option<SurfaceId>,
918 | |     ) -> Result<SurfaceId, CreateSurfaceError> {
    | |______________________________________________^

[ErichDonGubler]

@0323pin: You'll need to make similar cfg adjustments all the way up the call chain; you're the NetBSD expert here, so correct me if I'm wrong, but it seems your intention is to exclude drm (4) as a surface backend…unless you implement support for NetBSD's DRM system as a surface for OpenGL to render to, that is.