[clang] [llvm] [clang][SPIR-V] Add support for AMDGCN flavoured SPIRV (PR #89796)

[Alexey Bader via llvm-commits]

bader wrote:

@AlexVlx, do you think it's worth promoting [SPV_INTEL_inline_assembly](https://github.com/intel/llvm/blob/sycl/sycl/doc/design/spirv-extensions/SPV_INTEL_inline_assembly.asciidoc) and [SPV_INTEL_function_pointers](https://github.com/intel/llvm/blob/sycl/sycl/doc/design/spirv-extensions/SPV_INTEL_function_pointers.asciidoc) to Khronos extensions?

https://github.com/llvm/llvm-project/pull/89796