LLVM: update backend to LLVM 17

* LLVMConstSelect is removed (see
   https://discourse.llvm.org/t/rfc-remove-most-constant-expressions/63179)
 * a couple functions use uint64_t instead of int now which means we
   no longer need `@intCast`.

release/17.x branch, commit 8f4dd44097c9ae25dd203d5ac87f3b48f854bba8
6a07b7024aAndrew Kelley committed on 9/19/2023, 4:37:31 PMparent62a12e0
2 files changedLine totals unavailable