[Migrated] Shaders should not implicitly enable VulkanMemoryModel

Issue automatically imported from old repo: https://github.com/EmbarkStudios/rust-gpu/issues/1090
Old labels: t: bug
Originally creatd by Firestar99 on 2023-08-10T11:29:34Z

Expected Behaviour

rust-gpu compiling for any spirv-unknown-vulkan1.X target should not implicitly emit OpCapability VulkanMemoryModel in the resulting spv, instead one would need to call SpirvBuilder.capability(Capability::VulkanMemoryModel) to enable the VulkanMemoryModel explicitly.
This implicit enabling of that Capability can get in the way of 1:1 porting of glsl shaders to rust-gpu, as it also requires changes to the CPU code to enable the VulkanMemoryModel device feature. Switching to target spirv-unknown-spv1.X does remove the implicit capability from the shader, but it is disencouraged as it also "disables a bunch of rules in spirv-val".

Example & Steps To Reproduce

1. git clone https://github.com/Firestar99/rust-gpu-vulkano-example.git
2. In example/build.rs change TARGET from spirv-unknown-spv1.3 to spirv-unknown-vulkan1.2 (or any other vulkan version)
3. cargo run to see it fail when changes of 2. are applied

System Info

• Rust: nightly-2023-05-27
• OS: Ubuntu 23.04
• GPU: RADV REMBRANDT
• SPIR-V: SPIRV-Tools v2023.3 unknown hash, 2023-05-25T20:33:54

Start with the target handling around SpirvBuilder and the example/build.rs TARGET value described in the report. Reproduce with spirv-unknown-vulkan1.2 and inspect the resulting SPIR-V capability, comparing it with spirv-unknown-spv1.3. Done means Vulkan targets no longer emit VulkanMemoryModel implicitly, while explicit SpirvBuilder.capability(Capability::VulkanMemoryModel) still enables it.