[clang] [X86][test] Avoid writing to a potentially write-protected dir (PR #108525)

[Malay Sanghi via cfe-commits]

MalaySanghi wrote:

> I have submitted it as [a41bb71](https://github.com/llvm/llvm-project/commit/a41bb71f2216cef08ab04f1d730ae1701c145f3c) (with 3 files). Sorry for the race, but I want it working :)

Apologies for missing that file and thanks for taking this up.

https://github.com/llvm/llvm-project/pull/108525