[llvm] Fix X86InstrInfo.cpp build after llvm#160188

Author: jansvoboda11

llvm/lib/Target/X86/X86InstrInfo.cpp

@@ -44,6 +44,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetOptions.h"
+#include <atomic>
 #include <optional>
 
 using namespace llvm;