[BOLT][NFC] Make RepRet X86-specific (#88286)

Bolt's RepRet pass is x86-specific, no need to add it for non-x86
targets.

Author: urnathan

bolt/lib/Rewrite/BinaryPassManager.cpp

@@ -377,8 +377,9 @@ Error BinaryFunctionPassManager::runAllPasses(BinaryContext &BC) {
 
   Manager.registerPass(std::make_unique<NormalizeCFG>(PrintNormalized));
 
-  Manager.registerPass(std::make_unique<StripRepRet>(NeverPrint),
-                       opts::StripRepRet);
+  if (BC.isX86())
+    Manager.registerPass(std::make_unique<StripRepRet>(NeverPrint),
+                         opts::StripRepRet);
 
   Manager.registerPass(std::make_unique<IdenticalCodeFolding>(PrintICF),
                        opts::ICF);