[llvm] [Offload] Allow setting null arguments in olLaunchKernel and fix amdgpu handling for empty kernel arguments (PR #141958)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> However, more digging has revealed that even if you build a kernel with no arguments at the C level, when compiled at O0 a number of "hidden" arguments are added. 

More precisely they are there to begin with and optimized out if unused 

https://github.com/llvm/llvm-project/pull/141958