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

[Shilei Tian via llvm-commits]

shiltian wrote:

It seems like for some targets the compiler doesn't accept a 4-field triple. Why is that?

```
clang: error: version 'elf-unknown' in target triple 'hexagon-unknown-unknown-elf-unknown' is invalid
clang: error: version '-unknown' in target triple 'riscv64-unknown-linux-gnu-unknown' is invalid
```

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