[clang] [Coroutines][Test] Only run coro-elide-thinlto under x86_64-linux (PR #90672)

[Wei Wang via cfe-commits]

apolloww wrote:

https://lab.llvm.org/buildbot/#/builders/188/builds/45187

```
Error running ThinLTO backend: No available targets are compatible with triple "x86_64-unknown-linux"
```


https://github.com/llvm/llvm-project/pull/90672