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

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dyung wrote:

This test has been failing on bots for several hours now. Can we either get this fix in or the original change reverted to get the bots back to green? One failing bot is https://lab.llvm.org/buildbot/#/builders/280/builds/2876.

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