[ci] Specify -HV 2018 to dxc

[fornwall]

DX Compiler release for August 2023 was just released, and that made HLSL 2021 the default, breaking the CI build.

We currently generate hlsl that is not valid HLSL 2021, as there binary logic operators can only be used with scalars, so we need to change generation:

-  doit = vec && (ShouldIDoIt(vec) || !ShouldINotDoIt(vec));
+  doit = and(vec, or(ShouldIDoIt(vec), !ShouldINotDoIt(vec)));

While possible (changing countLeadingZeros() and select() writing is enough to pass CI), fxc does not support HLSL 2021 (and the and(), or() and select() intrinsics are only available in HLSL 2021).

So this PR specifies -HV 2018 to dxc, which was the previous default version.

[ErichDonGubler]

LGTM, minus the nit I left. 😊

[fornwall]

LGTM, minus the nit I left. 😊

Thanks! I don't see a nit comment, but was it perhaps the vim .swp file :)? If so, I removed it now (and proposed #2448)!

[ErichDonGubler]

Yep, that was it!

[ErichDonGubler]

@jimblandy: Mergeplz?

[teoxoy]

Ideally we should be forward compatible. Could you open a new issue to track this? I think we are running into this issue only for the select implementation; we can either take the language version as a parameter or inject a polyfill for vector conditions regardless of version.

[fornwall]

Ideally we should be forward compatible. Could you open a new issue to track this?

Created gfx-rs/wgpu#4498 for that!