This PR resolves the issue of the SPIR-V specification, requiring
Shader-coupled capabilities to read/write images in the OpenCL SPIR-V
environment, from the perspective of the LLVM SPIR-V backend. See
https://github.com/KhronosGroup/SPIRV-Headers/issues/487 for details and
discussion.
Current implementation correctly reproduces requirements of the SPIR-V
specification, however, since the requirements are problematic, out
current implementation blocks generation of valid SPIR-V code for
compute environments. This PR is to implement a solution discussed at
the SPIR-V WG to allow proceeding with generation of valid SPIR-V code
for the OpenCL environment and do not impact Vulkan environment at the
same time.