[clang] [llvm] [OffloadBundler] Rework the ctor of `OffloadTargetInfo` to support AMDGPU's generic target (PR #122629)

[Shilei Tian via llvm-commits]

shiltian wrote:

> Is there a way for us to still support 3-field triples and generic targets?

I can't come up with a better solution because we don't know how many `-` could exist in the generic target id. With that, fixating the "known" part (aka triple) would be reasonable. Do you have any suggestions?

> In the past we worked to allow 3-field triples as bundler inputs. I would be surprised if adding a 4-field restriction didn't break something internally.

I don't know if there is any project using `clang-offload-bundler` directly. If there is, and we decide to enforce it, we will have to update them as well.

https://github.com/llvm/llvm-project/pull/122629