[llvm] Add Option to Enable Dead Block Elimination in NVVMReflect (PR #144171)

[Yonah Goldberg via llvm-commits]

YonahGoldberg wrote:

We've had bugs filed with people compiling with nvcc -G on code that contains nvvmReflect and they get invalid PTX because of no nvvmReflect DCE cleanup. So it's not a corner case that that we turn this on, we will have it turned on for nvcc -G.

https://github.com/llvm/llvm-project/pull/144171