[llvm] [NVPTX] Use .common linkage for common globals (PR #84416)

[Artem Belevich via llvm-commits]

Artem-B wrote:

My understanding is that we should follow the "standard" linking rules for C++ and ELF objects. 

The quote in the PR description is all NVIDIA docs say about the `.common` directive. On the surface it does seem to match the standard behavior of common data, but I'm not very familiar with it. I mostly dealt with the problems it caused when some things were made common when they should not have been.

https://github.com/llvm/llvm-project/pull/84416