[llvm] [Analysis] Guard logf128 cst folding (PR #106543)

[Matthew Devereau via llvm-commits]

MDevereau wrote:

https://github.com/llvm/llvm-project/pull/104929/files#diff-84188b049af70f6ebc0b5a2aaa6287b2f84ca5486daa30efd18fe91140cda48c, which removes the check/target definition in Analysis completely and instead uses the more generic `add_compile_definitions` in `config-ix.cmake` to avoid setting target definitions for each target, is still in dispute about whether it can be merged in or not. If you want this immediately I'm happy to approve it, but when/if I rebase and reland https://github.com/llvm/llvm-project/pull/104929/, this change will almost certainly be removed unless there's a good reason for it.

https://github.com/llvm/llvm-project/pull/106543