[HLSL] Cbuffer declaration with array typedef crashes

[spall]

This code should compile, and if you use 'uint32_t4' directly in the cbuffer instead of the typedef it does.
https://godbolt.org/z/4nx4zsMdf

The type needs to be desugared before being cast to a ConstantArrayType.

[llvmbot]

@llvm/issue-subscribers-clang-codegen

Author: Sarah Spall (spall)

This code should compile, and if you use 'uint32_t4' directly in the cbuffer instead of the typedef it does. https://godbolt.org/z/4nx4zsMdf

The type needs to be desugared before being cast to a ConstantArrayType.