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

[Fraser Cormack via cfe-commits]

frasercrmck wrote:

An update on this: in adding a clang elementwise builtin for ldexp (and for clz/ctz) I found it necessary to first refactor the clang diagnostics. I opened a PR for it (https://github.com/llvm/llvm-project/pull/125673) which isn't getting much traction so that's slowing things down.

Unfortunately lots of other functions rely on ldexp so there's a bottleneck here.

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