Add Fuchsia support

[abarth]

Use the proper name for libvulkan.so on Fuchsia.

[MarijnS95]

https://doc.rust-lang.org/reference/conditional-compilation.html#target_os I'm surprised the official docs don't mention the existence of fuchsia :/. It's "only an example", but still.

[abarth]

Fuchsia is a Tier 2 supported OS for Rust:

https://doc.rust-lang.org/rustc/platform-support.html#tier-2

For context, I'm a Fuchsia OS developer. We'd like to switch over from vk_sys to ash in our Vulkan stack for Rust, but we ran into this minor issue.

[Ralith]

Fuchsia doesn't do the unixy .so.$MAJOR thing? Interesting; is this documented anywhere? Any way we can sensibly cover this in CI?

[Ralith]

Note that if you build ash with features = ["linked"], default-features = false, existing versions of ash should Just Work, and be less fragile at runtime besides.

[abarth]

Fuchsia doesn't do the unixy .so.$MAJOR thing?

Yes, we do that for most shared libraries. I'm not sure why libvulkan.so doesn't have a .$MAJOR suffix.

Interesting; is this documented anywhere?

https://fuchsia.dev/fuchsia-src/development/graphics/magma/concepts/vulkan?hl=en#buildtime_dependencies

Any way we can sensibly cover this in CI?

Not yet. We're working on that as part of our quest for Tier 1 support in Rust.

Note that if you build ash with features = ["linked"], default-features = false, existing versions of ash should Just Work, and be less fragile at runtime besides.

Ok, I'll give that a try.

[Ralith]

Yes, we do that for most shared libraries. I'm not sure why libvulkan.so doesn't have a .$MAJOR suffix.

Hmm, are you using the standard Khronos Vulkan loader? This may be a bug in the upstream build system, if so. I'm not entirely clear on the significance of respecting that pattern vs. not, but I figure it's probably worth being consistent with the system at large.

[MarijnS95]

@abarth any update on not using/having a .MAJOR suffix on Fuchsia?

[MarijnS95]

Looking at the linked Fuchsia docs it's still libvulkan.so without .MAJOR suffix; I'll merge this in for the 0.38 release.

[MarijnS95]

For cargo:rustc-link-lib=vulkan under the linked feature, this should keep working OOTB :)