[libclc] [libclc] Move __clc_ldexp to CLC library (PR #126078)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> > Yeah, amdgcn-amd-amdhsa should be roughly equivalent to amdgcn--
> 
> These are not equivalent

That's something I've been meaning to ask, the difference I know of right now is that `amdgcn--` will not create a ROCm toolchain so we don't do any of that. However, I don't know to what extent the `hsa` in the triple matters, because there's certain builtins that are tied to the implicit arguments. I never knew if that was an `hsa` thing or we considered the code object universal to `amdgcn--`. I mostly just meant that IR compiled with `amdgcn--` should be able to link with the HSA os version.

https://github.com/llvm/llvm-project/pull/126078