[llvm] [LLVM] Fix an ASAN error in `lookupLLVMIntrinsicByName` (PR #147444)

[Chandler Carruth via llvm-commits]

https://github.com/chandlerc commented:

FWIW, LG... not a huge fan of the `getCSTring` API, but no strong opinion here.

But good to wait for the other reviewer as well.

https://github.com/llvm/llvm-project/pull/147444