[clang] Add -fuse-lipo option (PR #121231)

[Ashley Hauck via cfe-commits]

khyperia wrote:

> LGTM in general with a comment in test.
> 
> For discussion. Is it better if the option supplies the full path to lipo or just the name? Full path seems to be easy to use, but might deserve a warning if the tool doesn't exist. If just the name, it might be better to rename the option to something like `-fuse-lipo-program=`.

As a prefix: I am a new contributor, if you or someone else experienced has an opinion here I will gladly blindly follow it.

I tried to take precedence from `-fuse-ld` and `--ld-path`, so `-fuse-lipo` takes a name, and a hypothetical future `--lipo-path` would be a full path. Perhaps these are only named this way due to legacy compatibility though, and new naming conventions should be something else, `fuse-lipo-program` as you say? I don't know the history and context here. Let me know what I should do!

> Nit: Add a test case to check when the flag is not supplied.

Pushed

https://github.com/llvm/llvm-project/pull/121231