[llvm] [offload] Extend LIT infrastructure to allow using more tools (PR #124636)

[Shilei Tian via llvm-commits]

shiltian wrote:

> It's dumped in `--save-temps` but I'd have to guess the file name which seems flaky.

I'm not sure this is right. The save temp file name should be determined.

You can even put some pre compiled stuff in `clang/test/Tooling/Inputs/` and simple just use it as input.

https://github.com/llvm/llvm-project/pull/124636