[llvm] [llvm-exegesis] Add support for pinning benchmarking process to a CPU (PR #85168)

[Clement Courbet via llvm-commits]

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@@ -384,6 +393,31 @@ class SubProcessFunctionExecutorImpl
     return make_error<SnippetSignal>(ChildSignalInfo.si_signo);
   }
 
+  void setCPUAffinityIfRequested() const {
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legrosbuffle wrote:

[nit] `static void setCPUAffinity(int) {` here, and `if (BenchmarkProcessCPU.has_value()) { setCPUAffinity(*value); }` at the call site.

https://github.com/llvm/llvm-project/pull/85168