[llvm] [JIT][X86] Respect `JITDUMP_USE_ARCH_TIMESTAMP` environment variable (PR #146085)

[Cody Tapscott via llvm-commits]

topolarity wrote:

> Do you not need to change anything in JITLoaderPerf?

Thanks! I didn't notice there was that implementation that needed updating.

https://github.com/llvm/llvm-project/pull/146085