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

[Yonah Goldberg via llvm-commits]

YonahGoldberg wrote:

@Artem-B I know you're OOO, but to update the bug and for when you get back, I added a flag `-nvvm-reflect-dce` to turn on this feature conditionally.

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