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

[Mikhail Goncharov via cfe-commits]

metaflow wrote:

I have submitted it as a41bb71f2216cef08ab04f1d730ae1701c145f3c (with 3 files). Sorry for the race, but I want it working :)

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