[lld] [llvm] [llvm][lld][NFC] Avoid reopening namespace std (PR #96450)

[David Blaikie via llvm-commits]

dwblaikie wrote:

If this works, I think it's a good idea for a couple of reasons:
1) Less chance of defining something else in namespace `std` by accident
2) Less chance of accidentally defining a new thing (well, I guess since it's a specialization that's not possible...) - same as the LLVM style rule... hmm, I thought we had a rule that encouraged function definitions to not use a `namespace x {` but instead `void x::y() { }` - because that helps ensure the definition is a definition for a prior declaration (otherwise it fails to compile)

https://github.com/llvm/llvm-project/pull/96450