[clang] Pass -offload-lto instead of -lto for cuda/hip kernels (PR #125243)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 requested changes to this pull request.

I don't understand the motivation for this, it is intentionally passing `-flto` because this is *not* an offloading compile job. This flag is mostly here for convenience, but it's not strictly necessary because the Nvlink job does LTO if it finds bitcode, so this just replaces an optional flag with a no-op.

https://github.com/llvm/llvm-project/pull/125243