spirv-val seems to be overly strict with subgroup builtins

[wingertge]

I recently switched to builtin structs but am now getting validation errors for SubgroupLocalInvocationId.

Validation Error: [ VUID-VkShaderModuleCreateInfo-pCode-08737 ] | MessageID = 0xa5625282
vkCreateShaderModule(): pCreateInfo->pCode (spirv-val produced an error):
BuiltIn SubgroupLocalInvocationId cannot be used as a member decoration
  %_struct_18 = OpTypeStruct %uint %uint

Command to reproduce:
        spirv-val <input.spv> --relax-block-layout --uniform-buffer-standard-layout --workgroup-scalar-block-layout --allow-localsizeid --allow-offset-texture-operand --allow-vulkan-32-bit-bitwise --target-env vulkan1.3

The Vulkan spec states: If pCode is a pointer to SPIR-V code, pCode must adhere to the validation rules described by the Validation Rules within a Module section of the SPIR-V Environment appendix (https://docs.vulkan.org/spec/latest/chapters/shaders.html#VUID-VkShaderModuleCreateInfo-pCode-08737)

I traced the code path to the code introduced in this PR 7 years ago.
I cannot find any validation rule for this, and there is no VUID attached.

The simple fix would be to remove the check that disallows member decorations, but I'd like to make sure I didn't somehow miss the rule that requires this first.

[alan-baker]

There is an open Khronos vulkan issue about this, but reality is that not all builtins can be placed in a block. If glslang doesn't emit it the builtin in a block, assume it is invalid. Sorry for the spec ambiguity.